EX-10.3



 Exhibit 10.3 

ACACIA COMMUNICATIONS, INC. 2009 STOCK PLAN 

NOTICE OF STOCK OPTION GRANT (INSTALLMENT
VESTING) 
 The Optionee has been granted the following option to purchase shares of the Common Stock of Acacia Communications, Inc.:

  

			
	Name of Optionee:	  	«Name»
		
	Total Number of Shares:	  	«TotalShares»
		
	Type of Option:	  	«ISO» Incentive Stock Option (ISO)
		
		  	«NSO» Nonstatutory Stock Option (NSO)
		
	Exercise Price per Share:	  	$«PricePerShare»
		
	Date of Grant:	  	«DateGrant»
		
	Date Exercisable:	  	This option may be exercised with respect to the first 20% of the Shares subject to this option when the Optionee completes 12 months of continuous Service beginning with the Vesting Commencement Date set forth below. This option
may be exercised with respect to an additional 1/60th of the Shares subject to this option when the Optionee completes each month of continuous Service thereafter.
		
	Vesting Commencement Date:	  	«VestComDate»
		
	Expiration Date:	  	«ExpDate». This option expires earlier if the Optionee’s Service terminates earlier, as provided in Section 6 of the Stock Option Agreement.

 By signing below, the Optionee and the Company agree that this option is granted under, and governed by the terms and
conditions of, the 2009 Stock Plan and the Stock Option Agreement. Both of these documents are attached to, and made a part of, this Notice of Stock Option Grant. Section 13 of the Stock Option Agreement includes important acknowledgements
of the Optionee. 
  

							
	OPTIONEE:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

		 		 	Title:	 	  









 THE OPTION GRANTED PURSUANT TO THIS AGREEMENT AND THE SHARES ISSUABLE UPON THE EXERCISE THEREOF HAVE NOT BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH
REGISTRATION IS NOT REQUIRED. 
 ACACIA COMMUNICATIONS, INC. 2009 STOCK
PLAN: 
 STOCK OPTION AGREEMENT (INSTALLMENT
VESTING) 
 SECTION 1. GRANT OF OPTION. 

(a) Option. On the terms and conditions set forth in the Notice of Stock Option Grant and this Agreement, the Company grants to the
Optionee on the Date of Grant the option to purchase at the Exercise Price the number of Shares set forth in the Notice of Stock Option Grant. The Exercise Price is agreed to be at least 100% of the Fair Market Value per Share on the Date of Grant
(110% of Fair Market Value if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). This option is intended to be an ISO or an NSO, as provided in the Notice of Stock Option Grant. 

(b) $100,000 Limitation. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it shall be deemed to be an
NSO to the extent (and only to the extent) required by the $100,000 annual limitation under Section 422(d) of the Code. 
 (c) Stock
Plan and Defined Terms. This option is granted pursuant to the Plan, a copy of which the Optionee acknowledges having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 14 of this Agreement. 
 SECTION 2. RIGHT TO EXERCISE. 

(a) Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or part of this
option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. 
 (b) Stockholder
Approval. Any other provision of this Agreement notwithstanding, no portion of this option shall be exercisable at any time prior to the approval of the Plan by the Company’s stockholders. 

SECTION 3. NO TRANSFER OR ASSIGNMENT OF OPTION. 

Except as otherwise provided in this Agreement, this option and the rights and privileges conferred hereby shall not be sold, pledged or
otherwise transferred (whether by operation of law or otherwise) and shall not be subject to sale under execution, attachment, levy or similar process. 







 SECTION 4. EXERCISE PROCEDURES. 

(a) Notice of Exercise. The Optionee or the Optionee’s representative may exercise this option by giving written notice to the
Company pursuant to Section 12(c). The notice shall specify the election to exercise this option, the number of Shares for which it is being exercised and the form of payment. The person exercising this option shall sign the notice. In the
event that this option is being exercised by the representative of the Optionee, the notice shall be accompanied by proof (satisfactory to the Company) of the representative’s right to exercise this option. The Optionee or the Optionee’s
representative shall deliver to the Company, at the time of giving the notice, payment in a form permissible under Section 5 for the full amount of the Purchase Price. 

(b) Issuance of Shares. After receiving a proper notice of exercise, the Company shall cause to be issued one or more certificates
evidencing the Shares for which this option has been exercised. Such Shares shall be registered (i) in the name of the person exercising this option, (ii) in the names of such person and his or her spouse as community property or as joint
tenants with the right of survivorship or (iii) with the Company’s consent, in the name of a revocable trust. The Company shall cause such certificates to be delivered to or upon the order of the person exercising this option. 

(c) Withholding Taxes. In the event that the Company determines that it is required to withhold any tax as a result of the exercise of
this option, the Optionee, as a condition to the exercise of this option, shall make arrangements satisfactory to the Company to enable it to satisfy all withholding requirements. The Optionee shall also make arrangements satisfactory to the Company
to enable it to satisfy any withholding requirements that may arise in connection with the disposition of Shares purchased by exercising this option. 

SECTION 5. PAYMENT FOR STOCK. 
 (a)
Cash. All or part of the Purchase Price may be paid in cash or cash equivalents. 
 (b) Surrender of Stock. At the discretion
of the Board of Directors, all or any part of the Purchase Price may be paid by surrendering, or attesting to the ownership of, Shares that are already owned by the Optionee. Such Shares shall be surrendered to the Company in good form for transfer
and shall be valued at their Fair Market Value as of the date when this option is exercised. 
 (c) Exercise/Sale. All or part of the
Purchase Price and any withholding taxes may be paid by the delivery (on a form prescribed by the Company) of an irrevocable direction to a securities broker approved by the Company to sell Shares and to deliver all or part of the sales proceeds to
the Company. However, payment pursuant to this Subsection (c) shall be permitted only if (i) Stock then is publicly traded and (ii) such payment does not violate applicable law. 

  
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 SECTION 6. TERM AND EXPIRATION. 

(a) Basic Term. This option shall in any event expire on the expiration date set forth in the Notice of Stock Option Grant, which date
is 10 years after the Date of Grant (five years after the Date of Grant if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). 

(b) Termination of Service (Except by Death). If the Optionee’s Service terminates for any reason other than death, then this
option shall expire on the earliest of the following occasions: 
 (i) The expiration date determined pursuant to
Subsection (a) above; 
 (ii) The date three months after the termination of the Optionee’s Service for any reason
other than Disability; or 
 (iii) The date six months after the termination of the Optionee’s Service by reason of
Disability. 
 The Optionee may exercise all or part of this option at any time before its expiration under the preceding sentence, but only to the extent
that this option had become exercisable before the Optionee’s Service terminated. When the Optionee’s Service terminates, this option shall expire immediately with respect to the number of Shares for which this option is not yet
exercisable. In the event that the Optionee dies after termination of Service but before the expiration of this option, all or part of this option may be exercised (prior to expiration) by the executors or administrators of the Optionee’s
estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s Service terminated. 

(c) Death of the Optionee. If the Optionee dies while in Service, then this option shall expire on the earlier of the following dates:

 (i) The expiration date determined pursuant to Subsection (a) above; or 

(ii) The date 12 months after the Optionee’s death. 

All or part of this option may be exercised at any time before its expiration under the preceding sentence by the executors or administrators of the
Optionee’s estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s death. When
the Optionee dies, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. 

(d) Part-Time Employment and Leaves of Absence. If the Optionee commences working on a part-time basis, then the Company may adjust the
vesting schedule set forth in the Notice of Stock Option Grant. If the Optionee goes on a leave of absence, then the 

  
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Company may adjust the vesting schedule set forth in the Notice of Stock Option Grant in accordance with the Company’s leave of absence policy or the terms of such leave. Except as provided
in the preceding sentence, Service shall be deemed to continue for any purpose under this Agreement while the Optionee is on a bona fide leave of absence, if (i) such leave was approved by the Company in writing and (ii) continued
crediting of Service for such purpose is expressly required by the terms of such leave or by applicable law (as determined by the Company). Service shall be deemed to terminate when such leave ends, unless the Optionee immediately returns to active
work. 
 (e) Notice Concerning ISO Treatment. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it
ceases to qualify for favorable tax treatment as an ISO to the extent that it is exercised: 
 (i) More than three months
after the date when the Optionee ceases to be an Employee for any reason other than death or permanent and total disability (as defined in Section 22(e)(3) of the Code); 

(ii) More than 12 months after the date when the Optionee ceases to be an Employee by reason of permanent and total disability
(as defined in Section 22(e)(3) of the Code); or 
 (iii) More than three months after the date when the Optionee has
been on a leave of absence for 90 days, unless the Optionee’s reemployment rights following such leave were guaranteed by statute or by contract. 

SECTION 7. RIGHT OF FIRST REFUSAL. 
 (a)
Right of First Refusal. In the event that the Optionee proposes to sell, pledge or otherwise transfer to a third party any Shares acquired under this Agreement, or any interest in such Shares, the Company shall have the Right of First Refusal
with respect to all (and not less than all) of such Shares. If the Optionee desires to transfer Shares acquired under this Agreement, the Optionee shall give a written Transfer Notice to the Company describing fully the proposed transfer, including
the number of Shares proposed to be transferred, the proposed transfer price, the name and address of the proposed Transferee and proof satisfactory to the Company that the proposed sale or transfer will not violate any applicable federal, State or
foreign securities laws. The Transfer Notice shall be signed both by the Optionee and by the proposed Transferee and must constitute a binding commitment of both parties to the transfer of the Shares. The Company shall have the right to purchase
all, and not less than all, of the Shares on the terms of the proposal described in the Transfer Notice (subject, however, to any change in such terms permitted under Subsection (b) below) by delivery of a notice of exercise of the Right of
First Refusal within 30 days after the date when the Transfer Notice was received by the Company. 
 (b) Transfer of Shares. If the
Company fails to exercise its Right of First Refusal within 30 days after the date when it received the Transfer Notice, the Optionee may, not later than 90 days following receipt of the Transfer Notice by the Company, conclude a transfer
of the Shares subject to the Transfer Notice on the terms and conditions described in the Transfer 

  
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Notice, provided that any such sale is made in compliance with applicable federal, State and foreign securities laws and not in violation of any other contractual restrictions to which the
Optionee is bound. Any proposed transfer on terms and conditions different from those described in the Transfer Notice, as well as any subsequent proposed transfer by the Optionee, shall again be subject to the Right of First Refusal and shall
require compliance with the procedure described in Subsection (a) above. If the Company exercises its Right of First Refusal, the parties shall consummate the sale of the Shares on the terms set forth in the Transfer Notice within 60 days
after the date when the Company received the Transfer Notice (or within such longer period as may have been specified in the Transfer Notice); provided, however, that in the event the Transfer Notice provided that payment for the Shares was to be
made in a form other than cash or cash equivalents paid at the time of transfer, the Company shall have the option of paying for the Shares with cash or cash equivalents equal to the present value of the consideration described in the Transfer
Notice. 
 (c) Additional or Exchanged Securities and Property. In the event of a merger or consolidation of the Company with or into
another entity, any other corporate reorganization, a stock split, the declaration of a stock dividend, the declaration of an extraordinary dividend payable in a form other than stock, a spin-off, an
adjustment in conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities, any securities or other property (including cash or cash equivalents) that are by reason of such transaction exchanged
for, or distributed with respect to, any Shares subject to this Section 7 shall immediately be subject to the Right of First Refusal. Appropriate adjustments to reflect the exchange or distribution of such securities or property shall be made
to the number and/or class of the Shares subject to this Section 7. 
 (d) Termination of Right of First Refusal. Any other
provision of this Section 7 notwithstanding, in the event that the Stock is readily tradable on an established securities market when the Optionee desires to transfer Shares, the Company shall have no Right of First Refusal, and the Optionee
shall have no obligation to comply with the procedures prescribed by Subsections (a) and (b) above. 
 (e) Permitted
Transfers. This Section 7 shall not apply to (i) a transfer by beneficiary designation, will or intestate succession or (ii) a transfer to one or more members of the Optionee’s Immediate Family or to a trust established by
the Optionee for the benefit of the Optionee and/or one or more members of the Optionee’s Immediate Family, provided in either case that the Transferee agrees in writing on a form prescribed by the Company to be bound by all provisions of this
Agreement. If the Optionee transfers any Shares acquired under this Agreement, either under this Subsection (e) or after the Company has failed to exercise the Right of First Refusal, then this Agreement shall apply to the Transferee to the
same extent as to the Optionee. 
 (f) Termination of Rights as Stockholder. If the Company makes available, at the time and place
and in the amount and form provided in this Agreement, the consideration for the Shares to be purchased in accordance with this Section 7, then after such time the person from whom such Shares are to be purchased shall no longer have any rights
as a holder of such Shares (other than the right to receive payment of such consideration in accordance with this Agreement). Such Shares shall be deemed to have been purchased in accordance with the applicable provisions hereof, whether or not the
certificate(s) therefor have been delivered as required by this Agreement. 

  
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 (g) Assignment of Right of First Refusal. The Board of Directors may freely assign the
Company’s Right of First Refusal, in whole or in part. Any person who accepts an assignment of the Right of First Refusal from the Company shall assume all of the Company’s rights and obligations under this Section 7. 

SECTION 8. LEGALITY OF INITIAL ISSUANCE. 

No Shares shall be issued upon the exercise of this option unless and until the Company has determined that: 

(a) It and the Optionee have taken any actions required to register the Shares under the Securities Act or to perfect an
exemption from the registration requirements thereof; 
 (b) Any applicable listing requirement of any stock exchange or
other securities market on which Stock is listed has been satisfied; and 
 (c) Any other applicable provision of federal,
State or foreign law has been satisfied. 
 SECTION 9. NO REGISTRATION RIGHTS. 

The Company may, but shall not be obligated to, register or qualify the sale of Shares under the Securities Act or any other applicable law.
The Company shall not be obligated to take any affirmative action in order to cause the sale of Shares under this Agreement to comply with any law. 

SECTION 10. RESTRICTIONS ON TRANSFER OF SHARES. 

(a) Securities Law Restrictions. Regardless of whether the offering and sale of Shares under the Plan have been registered under the
Securities Act or have been registered or qualified under the securities laws of any State, the Company at its discretion may impose restrictions upon the sale, pledge or other transfer of such Shares (including the placement of appropriate legends
on stock certificates or the imposition of stop-transfer instructions) if, in the judgment of the Company, such restrictions are necessary or desirable in order to achieve compliance with the Securities Act,
the securities laws of any State or any other law. 
 (b) Market Stand-Off. In connection with any underwritten public offering by
the Company of its equity securities pursuant to an effective registration statement filed under the Securities Act, including the Company’s initial public offering, the Optionee or a Transferee shall not directly or indirectly sell, make any
short sale of, loan, hypothecate, pledge, offer, grant or sell any option or other contract for the purchase of, purchase any option or other contract for the sale of, or otherwise dispose of or transfer, or agree to engage in any of the foregoing
transactions with respect to, any Shares acquired under this Agreement without the prior written consent of the Company or its managing underwriter. Such restriction (the “Market Stand-Off”)


  
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shall be in effect for such period of time following the date of the final prospectus for the offering as may be requested by the Company or such underwriter. In no event, however, shall such
period exceed 180 days plus such additional period as may reasonably be requested by the Company or such underwriter to accommodate regulatory restrictions on (i) the publication or other distribution of research reports or (ii) analyst
recommendations and opinions, including (without limitation) the restrictions set forth in Rule 2711(f)(4) of the National Association of Securities Dealers and Rule 472(f)(4) of the New York Stock Exchange, as amended, or any similar
successor rules. The Market Stand-Off shall in any event terminate two years after the date of the Company’s initial public offering. In the event of the declaration of a stock dividend, a spin-off, a
stock split, an adjustment in conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities without receipt of consideration, any new, substituted or additional securities which are by reason of
such transaction distributed with respect to any Shares subject to the Market Stand-Off, or into which such Shares thereby become convertible, shall immediately be subject to the Market Stand-Off. In order to enforce the Market Stand-Off, the
Company may impose stop-transfer instructions with respect to the Shares acquired under this Agreement until the end of the applicable stand-off period. The Company’s underwriters shall be beneficiaries of the agreement set forth in this
Subsection (b). This Subsection (b) shall not apply to Shares registered in the public offering under the Securities Act. 
 (c)
Investment Intent at Grant. The Optionee represents and agrees that the Shares to be acquired upon exercising this option will be acquired for investment, and not with a view to the sale or distribution thereof. 

(d) Investment Intent at Exercise. In the event that the sale of Shares under the Plan is not registered under the Securities Act but
an exemption is available that requires an investment representation or other representation, the Optionee shall represent and agree at the time of exercise that the Shares being acquired upon exercising this option are being acquired for
investment, and not with a view to the sale or distribution thereof, and shall make such other representations as are deemed necessary or appropriate by the Company and its counsel. 

(e) Legends. All certificates evidencing Shares purchased under this Agreement shall bear the following legend: 

“THE SHARES REPRESENTED HEREBY MAY NOT BE SOLD, ASSIGNED, TRANSFERRED, ENCUMBERED OR IN ANY MANNER DISPOSED OF, EXCEPT IN COMPLIANCE WITH
THE TERMS OF A WRITTEN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER OF THE SHARES (OR THE PREDECESSOR IN INTEREST TO THE SHARES). SUCH AGREEMENT GRANTS TO THE COMPANY CERTAIN RIGHTS OF FIRST REFUSAL UPON AN ATTEMPTED TRANSFER OF THE
SHARES. THE SECRETARY OF THE COMPANY WILL UPON WRITTEN REQUEST FURNISH A COPY OF SUCH AGREEMENT TO THE HOLDER HEREOF WITHOUT CHARGE.” 

  
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 All certificates evidencing Shares purchased under this Agreement in an unregistered transaction shall bear the
following legend (and such other restrictive legends as are required or deemed advisable under the provisions of any applicable law): 

“THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR
OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.” 

(f) Removal of Legends. If, in the opinion of the Company and its counsel, any legend placed on a stock certificate representing Shares
sold under this Agreement is no longer required, the holder of such certificate shall be entitled to exchange such certificate for a certificate representing the same number of Shares but without such legend. 

(g) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth in this
Section 10 shall be conclusive and binding on the Optionee and all other persons. 
 SECTION 11. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 8(a) of the Plan, the terms of this option (including, without limitation, the number
and kind of Shares subject to this option and the Exercise Price) shall be adjusted as set forth in Section 8(a) of the Plan. In the event that the Company is a party to a merger or consolidation, this option shall be subject to the agreement
of merger or consolidation, as provided in Section 8(b) of the Plan. 
 SECTION 12. MISCELLANEOUS PROVISIONS. 

(a) Rights as a Stockholder. Neither the Optionee nor the Optionee’s representative shall have any rights as a stockholder with
respect to any Shares subject to this option until the Optionee or the Optionee’s representative becomes entitled to receive such Shares by filing a notice of exercise and paying the Purchase Price pursuant to Sections 4 and 5. 

(b) No Retention Rights. Nothing in this option or in the Plan shall confer upon the Optionee any right to continue in Service for any
period of specific duration or interfere with or otherwise restrict in any way the rights of the Company (or any Parent or Subsidiary employing or retaining the Optionee) or of the Optionee, which rights are hereby expressly reserved by each, to
terminate his or her Service at any time and for any reason, with or without cause. 
 (c) Notice. Any notice required by the terms
of this Agreement shall be given in writing. It shall be deemed effective upon (i) personal delivery, (ii) deposit with the United States Postal Service, by registered or certified mail, with postage and fees prepaid or (iii) deposit
with Federal Express Corporation, with shipping charges prepaid. Notice shall be addressed to the Company at its principal executive office and to the Optionee at the address that he or she most recently provided to the Company in accordance with
this Subsection (c). 
 (d) Modifications and Waivers. No provision of this Agreement shall be modified, waived or discharged
unless the modification, waiver or discharge is agreed to in writing and signed by the Optionee and by an authorized officer of the Company (other than the 

  
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Optionee). No waiver by either party of any breach of, or of compliance with, any condition or provision of this Agreement by the other party shall be considered a waiver of any other condition
or provision or of the same condition or provision at another time. 
 (e) Entire Agreement. The Notice of Stock Option Grant, this
Agreement and the Plan constitute the entire contract between the parties hereto with regard to the subject matter hereof. They supersede any other agreements, representations or understandings (whether oral or written and whether express or
implied) that relate to the subject matter hereof. 
 (f) Choice of Law. This Agreement shall be governed by, and construed in
accordance with, the laws of the State of Delaware, as such laws are applied to contracts entered into and performed in such State. 
 SECTION 13.
ACKNOWLEDGEMENTS OF THE OPTIONEE. 
 (a) Tax Consequences. The Optionee agrees that the Company does not have a duty to design or
administer the Plan or its other compensation programs in a manner that minimizes the Optionee’s tax liabilities. The Optionee shall not make any claim against the Company or its Board of Directors, officers or employees related to tax
liabilities arising from this option or the Optionee’s other compensation. In particular, the Optionee acknowledges that this option is exempt from Section 409A of the Code only if the Exercise Price is at least equal to the Fair Market
Value per Share on the Date of Grant. Since Shares are not traded on an established securities market, the determination of their Fair Market Value is made by the Board of Directors or by an independent valuation firm retained by the Company. The
Optionee acknowledges that there is no guarantee in either case that the Internal Revenue Service will agree with the valuation, and the Optionee shall not make any claim against the Company or its Board of Directors, officers or employees in the
event that the Internal Revenue Service asserts that the valuation was too low. 
 (b) Electronic Delivery of Documents. The Optionee
agrees to accept by email all documents relating to the Company, the Plan or this option and all other documents that the Company is required to deliver to its security holders (including, without limitation, disclosures that may be required by the
Securities and Exchange Commission). The Optionee also agrees that the Company may deliver these documents by posting them on a website maintained by the Company or by a third party under contract with the Company. If the Company posts these
documents on a website, it shall notify the Optionee by email of their availability. The Optionee acknowledges that he or she may incur costs in connection with electronic delivery, including the cost of accessing the internet and printing fees, and
that an interruption of internet access may interfere with his or her ability to access the documents. This consent shall remain in effect until this option expires or until the Optionee gives the Company written notice that it should deliver paper
documents. 
 (c) No Notice of Expiration Date. The Optionee agrees that the Company and its officers, employees, attorneys and
agents do not have any obligation to notify him or her prior to the expiration of this option pursuant to Section 6, regardless of whether this option will expire at the end of its full term or on an earlier date related to the termination of
the Optionee’s Service. The Optionee further agrees that he or she has the sole responsibility for monitoring the 

  
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expiration of this option and for exercising this option, if at all, before it expires. This Subsection (c) shall supersede any contrary representation that may have been made, orally or in
writing, by the Company or by an officer, employee, attorney or agent of the Company. 
 SECTION 14. DEFINITIONS. 

(a) “Agreement” shall mean this Stock Option Agreement. 

(b) “Board of Directors” shall mean the Board of Directors of the Company, as constituted from time to time or, if a
Committee has been appointed, such Committee. 
 (c) “Code” shall mean the Internal Revenue Code of 1986, as amended. 

(d) “Committee” shall mean a committee of the Board of Directors, as described in Section 2 of the Plan. 

(e) “Company” shall mean Acacia Communications, Inc., a Delaware corporation. 

(f) “Consultant” shall mean a person who performs bona fide services for the Company, a Parent or a Subsidiary as a
consultant or advisor, excluding Employees and Outside Directors. 
 (g) “Date of Grant” shall mean the date of grant
specified in the Notice of Stock Option Grant, which date shall be the later of (i) the date on which the Board of Directors resolved to grant this option or (ii) the first day of the Optionee’s Service. 

(h) “Disability” shall mean that the Optionee is unable to engage in any substantial gainful activity by reason of any
medically determinable physical or mental impairment. 
 (i) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (j) “Exercise Price”
shall mean the amount for which one Share may be purchased upon exercise of this option, as specified in the Notice of Stock Option Grant. 

(k) “Fair Market Value” shall mean the fair market value of a Share, as determined by the Board of Directors in good faith.
Such determination shall be conclusive and binding on all persons. 
 (l) “Immediate Family” shall mean any child,
stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling, mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law or sister-in-law and shall include adoptive relationships. 

(m) “ISO” shall mean an employee incentive stock option described in Section 422(b) of the Code. 

  
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 (n) “Notice of Stock Option Grant” shall mean the document so entitled to which
this Agreement is attached. 
 (o) “NSO” shall mean a stock option not described in Section 422(b) or 423(b) of
the Code. 
 (p) “Optionee” shall mean the person named in the Notice of Stock Option Grant. 

(q) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(r) “Parent” shall mean any corporation (other than the Company) in an unbroken chain of corporations ending with the
Company, if each of the corporations other than the Company owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. 

(s) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as in effect on the Date of Grant. 

(t) “Purchase Price” shall mean the Exercise Price multiplied by the number of Shares with respect to which this option is
being exercised. 
 (u) “Right of First Refusal” shall mean the Company’s right of first refusal described in
Section 7. 
 (v) “Securities Act” shall mean the Securities Act of 1933, as amended. 

(w) “Service” shall mean service as an Employee, Outside Director or Consultant. 

(x) “Share” shall mean one share of Stock, as adjusted in accordance with Section 8 of the Plan (if applicable). 

(y) “Stock” shall mean the Common Stock of the Company. 

(z) “Subsidiary” shall mean any corporation (other than the Company) in an unbroken chain of corporations beginning with the
Company, if each of the corporations other than the last corporation in the unbroken chain owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. 

(aa) “Transferee” shall mean any person to whom the Optionee has directly or indirectly transferred any Share acquired under
this Agreement. 
 (bb) “Transfer Notice” shall mean the notice of a proposed transfer of Shares described in
Section 7. 

  
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 ACACIA COMMUNICATIONS, INC. 2009
STOCK PLAN 
 NOTICE OF STOCK OPTION
GRANT 
 (INSTALLMENT VESTING, ACCELERATION) 

The Optionee has been granted the following option to purchase shares of the Common Stock of Acacia Communications, Inc.: 

 

			
	Name of Optionee:	 	«Name»
		
	Total Number of Shares:	 	«TotalShares»
		
	Type of Option:	 	«ISO» Incentive Stock Option (ISO)
		
		 	«NSO» Nonstatutory Stock Option (NSO)
		
	Exercise Price per Share:	 	$«PricePerShare»
		
	Date of Grant:	 	«DateGrant»
		
	Date Exercisable:	 	This option may be exercised with respect to the first 20% of the Shares subject to this option when the Optionee completes 12 months of continuous Service beginning with the Vesting Commencement Date set forth below. This option
may be exercised with respect to an additional 1/60th of the Shares subject to this option when the Optionee completes each month of continuous Service thereafter. This option may become exercisable on an accelerated basis under Section 2(a) of
the Stock Option Agreement.
		
	Vesting Commencement Date:	 	«VestComDate»
		
	Expiration Date:	 	«ExpDate». This option expires earlier if the Optionee’s Service terminates earlier, as provided in Section 6 of the Stock Option Agreement.

 By signing below, the Optionee and the Company agree that this option is granted under, and governed by the terms and
conditions of, the 2009 Stock Plan and the Stock Option Agreement. Both of these documents are attached to, and made a part of, this Notice of Stock Option Grant. Section 13 of the Stock Option Agreement includes important acknowledgements
of the Optionee. 
  

							
	OPTIONEE:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

		 		 	Title:	 	  









 THE OPTION GRANTED PURSUANT TO THIS AGREEMENT AND THE SHARES ISSUABLE UPON THE EXERCISE THEREOF HAVE NOT BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH
REGISTRATION IS NOT REQUIRED. 
 ACACIA COMMUNICATIONS, INC. 2009 STOCK
PLAN: 
 STOCK OPTION AGREEMENT (INSTALLMENT
VESTING) 
 SECTION 1. GRANT OF OPTION. 

(a) Option. On the terms and conditions set forth in the Notice of Stock Option Grant and this Agreement, the Company grants to the
Optionee on the Date of Grant the option to purchase at the Exercise Price the number of Shares set forth in the Notice of Stock Option Grant. The Exercise Price is agreed to be at least 100% of the Fair Market Value per Share on the Date of Grant
(110% of Fair Market Value if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). This option is intended to be an ISO or an NSO, as provided in the Notice of Stock Option Grant. 

(b) $100,000 Limitation. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it shall be deemed to be an
NSO to the extent (and only to the extent) required by the $100,000 annual limitation under Section 422(d) of the Code. 
 (c) Stock
Plan and Defined Terms. This option is granted pursuant to the Plan, a copy of which the Optionee acknowledges having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 14 of this Agreement. 
 SECTION 2. RIGHT TO EXERCISE. 

(a) Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or part of this
option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, if the Company is subject to a Change in Control before the Optionee’s Service terminates, then at all times after
the Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service. 

(b) Stockholder Approval. Any other provision of this Agreement notwithstanding, no portion of this option shall be exercisable at any
time prior to the approval of the Plan by the Company’s stockholders. 







 SECTION 3. NO TRANSFER OR ASSIGNMENT OF OPTION. 

Except as otherwise provided in this Agreement, this option and the rights and privileges conferred hereby shall not be sold, pledged or
otherwise transferred (whether by operation of law or otherwise) and shall not be subject to sale under execution, attachment, levy or similar process. 

SECTION 4. EXERCISE PROCEDURES. 
 (a)
Notice of Exercise. The Optionee or the Optionee’s representative may exercise this option by giving written notice to the Company pursuant to Section 12(c). The notice shall specify the election to exercise this option, the number
of Shares for which it is being exercised and the form of payment. The person exercising this option shall sign the notice. In the event that this option is being exercised by the representative of the Optionee, the notice shall be accompanied by
proof (satisfactory to the Company) of the representative’s right to exercise this option. The Optionee or the Optionee’s representative shall deliver to the Company, at the time of giving the notice, payment in a form permissible under
Section 5 for the full amount of the Purchase Price. 
 (b) Issuance of Shares. After receiving a proper notice of exercise, the
Company shall cause to be issued one or more certificates evidencing the Shares for which this option has been exercised. Such Shares shall be registered (i) in the name of the person exercising this option, (ii) in the names of such
person and his or her spouse as community property or as joint tenants with the right of survivorship or (iii) with the Company’s consent, in the name of a revocable trust. The Company shall cause such certificates to be delivered to or
upon the order of the person exercising this option. 
 (c) Withholding Taxes. In the event that the Company determines that it is
required to withhold any tax as a result of the exercise of this option, the Optionee, as a condition to the exercise of this option, shall make arrangements satisfactory to the Company to enable it to satisfy all withholding requirements. The
Optionee shall also make arrangements satisfactory to the Company to enable it to satisfy any withholding requirements that may arise in connection with the disposition of Shares purchased by exercising this option. 

SECTION 5. PAYMENT FOR STOCK. 
 (a)
Cash. All or part of the Purchase Price may be paid in cash or cash equivalents. 
 (b) Surrender of Stock. At the discretion
of the Board of Directors, all or any part of the Purchase Price may be paid by surrendering, or attesting to the ownership of, Shares that are already owned by the Optionee. Such Shares shall be surrendered to the Company in good form for transfer
and shall be valued at their Fair Market Value as of the date when this option is exercised. 
 (c) Exercise/Sale. All or part of the
Purchase Price and any withholding taxes may be paid by the delivery (on a form prescribed by the Company) of an irrevocable direction to a securities broker approved by the Company to sell Shares and to deliver all or part


  
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of the sales proceeds to the Company. However, payment pursuant to this Subsection (c) shall be permitted only if (i) Stock then is publicly traded and (ii) such payment does not
violate applicable law. 
 SECTION 6. TERM AND EXPIRATION. 

(a) Basic Term. This option shall in any event expire on the expiration date set forth in the Notice of Stock Option Grant, which date
is 10 years after the Date of Grant (five years after the Date of Grant if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). 

(b) Termination of Service (Except by Death). If the Optionee’s Service terminates for any reason other than death, then this
option shall expire on the earliest of the following occasions: 
 (i) The expiration date determined pursuant to
Subsection (a) above; 
 (ii) The date three months after the termination of the Optionee’s Service for any reason
other than Disability; or 
 (iii) The date six months after the termination of the Optionee’s Service by reason of
Disability. 
 The Optionee may exercise all or part of this option at any time before its expiration under the preceding sentence, but only to the extent
that this option had become exercisable before the Optionee’s Service terminated. When the Optionee’s Service terminates, this option shall expire immediately with respect to the number of Shares for which this option is not yet
exercisable. In the event that the Optionee dies after termination of Service but before the expiration of this option, all or part of this option may be exercised (prior to expiration) by the executors or administrators of the Optionee’s
estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s Service terminated. 

(c) Death of the Optionee. If the Optionee dies while in Service, then this option shall expire on the earlier of the following dates:

 (i) The expiration date determined pursuant to Subsection (a) above; or 

(ii) The date 12 months after the Optionee’s death. 

All or part of this option may be exercised at any time before its expiration under the preceding sentence by the executors or administrators of the
Optionee’s estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s death. When
the Optionee dies, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. 

  
 3 








 (d) Part-Time Employment and Leaves of Absence. If the Optionee commences working on a
part-time basis, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option Grant. If the Optionee goes on a leave of absence, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option
Grant in accordance with the Company’s leave of absence policy or the terms of such leave. Except as provided in the preceding sentence, Service shall be deemed to continue for any purpose under this Agreement while the Optionee is on a bona
fide leave of absence, if (i) such leave was approved by the Company in writing and (ii) continued crediting of Service for such purpose is expressly required by the terms of such leave or by applicable law (as determined by the
Company). Service shall be deemed to terminate when such leave ends, unless the Optionee immediately returns to active work. 
 (e)
Notice Concerning ISO Treatment. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it ceases to qualify for favorable tax treatment as an ISO to the extent that it is exercised: 

(i) More than three months after the date when the Optionee ceases to be an Employee for any reason other than death or
permanent and total disability (as defined in Section 22(e)(3) of the Code); 
 (ii) More than 12 months after the date
when the Optionee ceases to be an Employee by reason of permanent and total disability (as defined in Section 22(e)(3) of the Code); or 

(iii) More than three months after the date when the Optionee has been on a leave of absence for 90 days, unless the
Optionee’s reemployment rights following such leave were guaranteed by statute or by contract. 
 SECTION 7. RIGHT OF FIRST REFUSAL. 

(a) Right of First Refusal. In the event that the Optionee proposes to sell, pledge or otherwise transfer to a third party any Shares
acquired under this Agreement, or any interest in such Shares, the Company shall have the Right of First Refusal with respect to all (and not less than all) of such Shares. If the Optionee desires to transfer Shares acquired under this Agreement,
the Optionee shall give a written Transfer Notice to the Company describing fully the proposed transfer, including the number of Shares proposed to be transferred, the proposed transfer price, the name and address of the proposed Transferee and
proof satisfactory to the Company that the proposed sale or transfer will not violate any applicable federal, State or foreign securities laws. The Transfer Notice shall be signed both by the Optionee and by the proposed Transferee and must
constitute a binding commitment of both parties to the transfer of the Shares. The Company shall have the right to purchase all, and not less than all, of the Shares on the terms of the proposal described in the Transfer Notice (subject, however, to
any change in such terms permitted under Subsection (b) below) by delivery of a notice of exercise of the Right of First Refusal within 30 days after the date when the Transfer Notice was received by the Company. 

  
 4 








 (b) Transfer of Shares. If the Company fails to exercise its Right of First Refusal within
30 days after the date when it received the Transfer Notice, the Optionee may, not later than 90 days following receipt of the Transfer Notice by the Company, conclude a transfer of the Shares subject to the Transfer Notice on the terms
and conditions described in the Transfer Notice, provided that any such sale is made in compliance with applicable federal, State and foreign securities laws and not in violation of any other contractual restrictions to which the Optionee is bound.
Any proposed transfer on terms and conditions different from those described in the Transfer Notice, as well as any subsequent proposed transfer by the Optionee, shall again be subject to the Right of First Refusal and shall require compliance with
the procedure described in Subsection (a) above. If the Company exercises its Right of First Refusal, the parties shall consummate the sale of the Shares on the terms set forth in the Transfer Notice within 60 days after the date when the
Company received the Transfer Notice (or within such longer period as may have been specified in the Transfer Notice); provided, however, that in the event the Transfer Notice provided that payment for the Shares was to be made in a form other than
cash or cash equivalents paid at the time of transfer, the Company shall have the option of paying for the Shares with cash or cash equivalents equal to the present value of the consideration described in the Transfer Notice. 

(c) Additional or Exchanged Securities and Property. In the event of a merger or consolidation of the Company with or into another
entity, any other corporate reorganization, a stock split, the declaration of a stock dividend, the declaration of an extraordinary dividend payable in a form other than stock, a spin-off, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities, any securities or other property (including cash or cash equivalents) that are by reason of such transaction exchanged for, or
distributed with respect to, any Shares subject to this Section 7 shall immediately be subject to the Right of First Refusal. Appropriate adjustments to reflect the exchange or distribution of such securities or property shall be made to the
number and/or class of the Shares subject to this Section 7. 
 (d) Termination of Right of First Refusal. Any other provision
of this Section 7 notwithstanding, in the event that the Stock is readily tradable on an established securities market when the Optionee desires to transfer Shares, the Company shall have no Right of First Refusal, and the Optionee shall have
no obligation to comply with the procedures prescribed by Subsections (a) and (b) above. 
 (e) Permitted Transfers. This
Section 7 shall not apply to (i) a transfer by beneficiary designation, will or intestate succession or (ii) a transfer to one or more members of the Optionee’s Immediate Family or to a trust established by the Optionee for the
benefit of the Optionee and/or one or more members of the Optionee’s Immediate Family, provided in either case that the Transferee agrees in writing on a form prescribed by the Company to be bound by all provisions of this Agreement. If the
Optionee transfers any Shares acquired under this Agreement, either under this Subsection (e) or after the Company has failed to exercise the Right of First Refusal, then this Agreement shall apply to the Transferee to the same extent as to the
Optionee. 
 (f) Termination of Rights as Stockholder. If the Company makes available, at the time and place and in the amount and
form provided in this Agreement, the consideration 

  
 5 








 
for the Shares to be purchased in accordance with this Section 7, then after such time the person from whom such Shares are to be purchased shall no longer have any rights as a holder of
such Shares (other than the right to receive payment of such consideration in accordance with this Agreement). Such Shares shall be deemed to have been purchased in accordance with the applicable provisions hereof, whether or not the certificate(s)
therefor have been delivered as required by this Agreement. 
 (g) Assignment of Right of First Refusal. The Board of Directors may
freely assign the Company’s Right of First Refusal, in whole or in part. Any person who accepts an assignment of the Right of First Refusal from the Company shall assume all of the Company’s rights and obligations under this
Section 7. 
 SECTION 8. LEGALITY OF INITIAL ISSUANCE. 

No Shares shall be issued upon the exercise of this option unless and until the Company has determined that: 

(a) It and the Optionee have taken any actions required to register the Shares under the Securities Act or to perfect an
exemption from the registration requirements thereof; 
 (b) Any applicable listing requirement of any stock exchange or
other securities market on which Stock is listed has been satisfied; and 
 (c) Any other applicable provision of federal,
State or foreign law has been satisfied. 
 SECTION 9. NO REGISTRATION RIGHTS. 

The Company may, but shall not be obligated to, register or qualify the sale of Shares under the Securities Act or any other applicable law.
The Company shall not be obligated to take any affirmative action in order to cause the sale of Shares under this Agreement to comply with any law. 

SECTION 10. RESTRICTIONS ON TRANSFER OF SHARES. 

(a) Securities Law Restrictions. Regardless of whether the offering and sale of Shares under the Plan have been registered under the
Securities Act or have been registered or qualified under the securities laws of any State, the Company at its discretion may impose restrictions upon the sale, pledge or other transfer of such Shares (including the placement of appropriate legends
on stock certificates or the imposition of stop-transfer instructions) if, in the judgment of the Company, such restrictions are necessary or desirable in order to achieve compliance with the Securities Act,
the securities laws of any State or any other law. 
 (b) Market Stand-Off. In connection with any underwritten public offering by
the Company of its equity securities pursuant to an effective registration statement filed under the Securities Act, including the Company’s initial public offering, the Optionee or a Transferee shall not directly or indirectly sell, make any
short sale of, loan, hypothecate, pledge, offer, grant 

  
 6 








 
or sell any option or other contract for the purchase of, purchase any option or other contract for the sale of, or otherwise dispose of or transfer, or agree to engage in any of the foregoing
transactions with respect to, any Shares acquired under this Agreement without the prior written consent of the Company or its managing underwriter. Such restriction (the “Market Stand-Off”) shall be in effect for such period of time
following the date of the final prospectus for the offering as may be requested by the Company or such underwriter. In no event, however, shall such period exceed 180 days plus such additional period as may reasonably be requested by the Company or
such underwriter to accommodate regulatory restrictions on (i) the publication or other distribution of research reports or (ii) analyst recommendations and opinions, including (without limitation) the restrictions set forth in
Rule 2711(f)(4) of the National Association of Securities Dealers and Rule 472(f)(4) of the New York Stock Exchange, as amended, or any similar successor rules. The Market Stand-Off shall in any event terminate two years after the date of
the Company’s initial public offering. In the event of the declaration of a stock dividend, a spin-off, a stock split, an adjustment in conversion ratio, a recapitalization or a similar transaction
affecting the Company’s outstanding securities without receipt of consideration, any new, substituted or additional securities which are by reason of such transaction distributed with respect to any Shares subject to the Market Stand-Off, or
into which such Shares thereby become convertible, shall immediately be subject to the Market Stand-Off. In order to enforce the Market Stand-Off, the Company may impose stop-transfer instructions with respect to the Shares acquired under this
Agreement until the end of the applicable stand-off period. The Company’s underwriters shall be beneficiaries of the agreement set forth in this Subsection (b). This Subsection (b) shall not apply to Shares registered in the public
offering under the Securities Act. 
 (c) Investment Intent at Grant. The Optionee represents and agrees that the Shares to be
acquired upon exercising this option will be acquired for investment, and not with a view to the sale or distribution thereof. 
 (d)
Investment Intent at Exercise. In the event that the sale of Shares under the Plan is not registered under the Securities Act but an exemption is available that requires an investment representation or other representation, the Optionee shall
represent and agree at the time of exercise that the Shares being acquired upon exercising this option are being acquired for investment, and not with a view to the sale or distribution thereof, and shall make such other representations as are
deemed necessary or appropriate by the Company and its counsel. 
 (e) Legends. All certificates evidencing Shares purchased under
this Agreement shall bear the following legend: 
 “THE SHARES REPRESENTED HEREBY MAY NOT BE SOLD, ASSIGNED, TRANSFERRED, ENCUMBERED OR
IN ANY MANNER DISPOSED OF, EXCEPT IN COMPLIANCE WITH THE TERMS OF A WRITTEN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER OF THE SHARES (OR THE PREDECESSOR IN INTEREST TO THE SHARES). SUCH AGREEMENT GRANTS TO THE COMPANY CERTAIN RIGHTS OF
FIRST REFUSAL UPON AN ATTEMPTED TRANSFER OF THE SHARES. THE SECRETARY OF THE COMPANY WILL UPON WRITTEN REQUEST FURNISH A COPY OF SUCH AGREEMENT TO THE HOLDER HEREOF WITHOUT CHARGE.” 

  
 7 








 All certificates evidencing Shares purchased under this Agreement in an unregistered transaction shall bear the
following legend (and such other restrictive legends as are required or deemed advisable under the provisions of any applicable law): 

“THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR
OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.” 

(f) Removal of Legends. If, in the opinion of the Company and its counsel, any legend placed on a stock certificate representing Shares
sold under this Agreement is no longer required, the holder of such certificate shall be entitled to exchange such certificate for a certificate representing the same number of Shares but without such legend. 

(g) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth in this
Section 10 shall be conclusive and binding on the Optionee and all other persons. 
 SECTION 11. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 8(a) of the Plan, the terms of this option (including, without limitation, the number
and kind of Shares subject to this option and the Exercise Price) shall be adjusted as set forth in Section 8(a) of the Plan. In the event that the Company is a party to a merger or consolidation, this option shall be subject to the agreement
of merger or consolidation, as provided in Section 8(b) of the Plan. 
 SECTION 12. MISCELLANEOUS PROVISIONS. 

(a) Rights as a Stockholder. Neither the Optionee nor the Optionee’s representative shall have any rights as a stockholder with
respect to any Shares subject to this option until the Optionee or the Optionee’s representative becomes entitled to receive such Shares by filing a notice of exercise and paying the Purchase Price pursuant to Sections 4 and 5. 

(b) No Retention Rights. Nothing in this option or in the Plan shall confer upon the Optionee any right to continue in Service for any
period of specific duration or interfere with or otherwise restrict in any way the rights of the Company (or any Parent or Subsidiary employing or retaining the Optionee) or of the Optionee, which rights are hereby expressly reserved by each, to
terminate his or her Service at any time and for any reason, with or without cause. 
 (c) Notice. Any notice required by the terms
of this Agreement shall be given in writing. It shall be deemed effective upon (i) personal delivery, (ii) deposit with the United States Postal Service, by registered or certified mail, with postage and fees prepaid or (iii) deposit
with Federal Express Corporation, with shipping charges prepaid. Notice shall be addressed to the Company at its principal executive office and to the Optionee at the address that he or she most recently provided to the Company in accordance with
this Subsection (c). 

  
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 (d) Modifications and Waivers. No provision of this Agreement shall be modified, waived or
discharged unless the modification, waiver or discharge is agreed to in writing and signed by the Optionee and by an authorized officer of the Company (other than the Optionee). No waiver by either party of any breach of, or of compliance with, any
condition or provision of this Agreement by the other party shall be considered a waiver of any other condition or provision or of the same condition or provision at another time. 

(e) Entire Agreement. The Notice of Stock Option Grant, this Agreement and the Plan constitute the entire contract between the parties
hereto with regard to the subject matter hereof. They supersede any other agreements, representations or understandings (whether oral or written and whether express or implied) that relate to the subject matter hereof. 

(f) Choice of Law. This Agreement shall be governed by, and construed in accordance with, the laws of the State of Delaware, as such
laws are applied to contracts entered into and performed in such State. 
 SECTION 13. ACKNOWLEDGEMENTS OF THE OPTIONEE. 

(a) Tax Consequences. The Optionee agrees that the Company does not have a duty to design or administer the Plan or its other
compensation programs in a manner that minimizes the Optionee’s tax liabilities. The Optionee shall not make any claim against the Company or its Board of Directors, officers or employees related to tax liabilities arising from this option or
the Optionee’s other compensation. In particular, the Optionee acknowledges that this option is exempt from Section 409A of the Code only if the Exercise Price is at least equal to the Fair Market Value per Share on the Date of Grant.
Since Shares are not traded on an established securities market, the determination of their Fair Market Value is made by the Board of Directors or by an independent valuation firm retained by the Company. The Optionee acknowledges that there is no
guarantee in either case that the Internal Revenue Service will agree with the valuation, and the Optionee shall not make any claim against the Company or its Board of Directors, officers or employees in the event that the Internal Revenue Service
asserts that the valuation was too low. 
 (b) Electronic Delivery of Documents. The Optionee agrees to accept by email all documents
relating to the Company, the Plan or this option and all other documents that the Company is required to deliver to its security holders (including, without limitation, disclosures that may be required by the Securities and Exchange Commission). The
Optionee also agrees that the Company may deliver these documents by posting them on a website maintained by the Company or by a third party under contract with the Company. If the Company posts these documents on a website, it shall notify the
Optionee by email of their availability. The Optionee acknowledges that he or she may incur costs in connection with electronic delivery, including the cost of accessing the internet and printing fees, and that an interruption of internet access may
interfere with his or her ability to access the documents. This consent shall remain in effect until this option expires or until the Optionee gives the Company written notice that it should deliver paper documents. 

(c) No Notice of Expiration Date. The Optionee agrees that the Company and its officers, employees, attorneys and agents do not have
any obligation to notify him or her 

  
 9 








 
prior to the expiration of this option pursuant to Section 6, regardless of whether this option will expire at the end of its full term or on an earlier date related to the termination of
the Optionee’s Service. The Optionee further agrees that he or she has the sole responsibility for monitoring the expiration of this option and for exercising this option, if at all, before it expires. This Subsection (c) shall supersede
any contrary representation that may have been made, orally or in writing, by the Company or by an officer, employee, attorney or agent of the Company. 

SECTION 14. DEFINITIONS. 
 (a)
“Agreement” shall mean this Stock Option Agreement. 
 (b) “Board of Directors” shall mean the Board of
Directors of the Company, as constituted from time to time or, if a Committee has been appointed, such Committee. 
 (c)
“Cause” shall mean a good faith determination by the Board of Directors of any of the following: 
 (i) An
unauthorized use or disclosure by the Optionee of the Company’s confidential information or trade secrets, which use or disclosure causes material harm to the Company; 

(ii) A material breach by the Optionee of any material agreement between the Purchaser and the Company; 

(iii) A material failure by the Optionee to comply with the Company’s written policies or rules after receiving written
notification of such failure from the Board of Directors; 
 (iv) The Optionee’s conviction of, or plea of
“guilty” or “no contest” to, a felony under the laws of the United States or any state thereof; 
 (v)
The Optionee’s gross negligence or willful misconduct in the course of performing Service; 
 (vi) A continuing failure
by the Optionee to perform reasonably assigned duties after receiving written notification of such failure from the Board of Directors; or 

(vii) A failure by the Optionee to cooperate in good faith with a governmental or internal investigation of the Company or its
directors, officers or employees, if the Company has requested the Purchaser’s cooperation 
 (d) “Change in Control”
shall mean (i) the consummation of a merger or consolidation of the Company with or into another entity or (ii) the sale, transfer or other disposition of all or substantially all of the Company’s assets. The foregoing
notwithstanding, a merger or consolidation of the Company shall not constitute a “Change in Control” if immediately after such merger or consolidation a majority of the voting power of the capital stock of the continuing or surviving
entity, or any direct or indirect parent corporation of such 

  
 10 








 
continuing or surviving entity, will be owned by persons who were the Company’s stockholders immediately prior to such merger or consolidation in substantially the same proportions as their
ownership of the voting power of the Company’s capital stock immediately prior to such merger or consolidation. 
 (e)
“Code” shall mean the Internal Revenue Code of 1986, as amended. 
 (f) “Committee” shall mean a committee
of the Board of Directors, as described in Section 2 of the Plan. 
 (g) “Company” shall mean Acacia Communications,
Inc., a Delaware corporation. 
 (h) “Consultant” shall mean a person who performs bona fide services for the Company, a
Parent or a Subsidiary as a consultant or advisor, excluding Employees and Outside Directors. 
 (i) “Date of Grant” shall
mean the date of grant specified in the Notice of Stock Option Grant, which date shall be the later of (i) the date on which the Board of Directors resolved to grant this option or (ii) the first day of the Optionee’s Service. 

(j) “Disability” shall mean that the Optionee is unable to engage in any substantial gainful activity by reason of any
medically determinable physical or mental impairment. 
 (k) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (l) “Exercise Price”
shall mean the amount for which one Share may be purchased upon exercise of this option, as specified in the Notice of Stock Option Grant. 

(m) “Fair Market Value” shall mean the fair market value of a Share, as determined by the Board of Directors in good faith.
Such determination shall be conclusive and binding on all persons. 
 (n) “Immediate Family” shall mean any child,
stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling, mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law or sister-in-law and shall include adoptive relationships. 

(o) “Involuntary Termination” shall mean the termination of the Optionee’s Service by reason of: 

(i) The involuntary discharge of the Optionee by the Company (or the Parent or Subsidiary employing him) for reasons other than
Cause; or 
 (ii) The voluntary resignation of the Optionee following any of the following events, if such event occurs
without the consent of the Optionee: (A) a change in the Optionee’s position with the Company (or the Parent or 

  
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Subsidiary employing him or her) that materially reduces his or her level of authority or responsibility (provided that the Optionee’s level of authority or responsibility shall not be
deemed to be reduced merely because there are additional employees more senior to the Optionee as a result of the Change in Control), (B) a reduction in the Optionee’s base salary by more than 10%, unless such reduction is made in
connection with a commensurate reduction in the compensation of employees of the Company generally, or (C) receipt of notice that the Optionee’s principal workplace will be relocated more than 50 miles 

(p) “ISO” shall mean an employee incentive stock option described in Section 422(b) of the Code. 

(q) “Notice of Stock Option Grant” shall mean the document so entitled to which this Agreement is attached. 

(r) “NSO” shall mean a stock option not described in Section 422(b) or 423(b) of the Code. 

(s) “Optionee” shall mean the person named in the Notice of Stock Option Grant. 

(t) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(u) “Parent” shall mean any corporation (other than the Company) in an unbroken chain of corporations ending with the
Company, if each of the corporations other than the Company owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. 

(v) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as in effect on the Date of Grant. 

(w) “Purchase Price” shall mean the Exercise Price multiplied by the number of Shares with respect to which this option is
being exercised. 
 (x) “Right of First Refusal” shall mean the Company’s right of first refusal described in
Section 7. 
 (y) “Securities Act” shall mean the Securities Act of 1933, as amended. 

(z) “Service” shall mean service as an Employee, Outside Director or Consultant. 

(aa) “Share” shall mean one share of Stock, as adjusted in accordance with Section 8 of the Plan (if applicable). 

(bb) “Stock” shall mean the Common Stock of the Company. 

  
 12 








 (cc) “Subsidiary” shall mean any corporation (other than the Company) in an
unbroken chain of corporations beginning with the Company, if each of the corporations other than the last corporation in the unbroken chain owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the
other corporations in such chain. 
 (dd) “Transferee” shall mean any person to whom the Optionee has directly or
indirectly transferred any Share acquired under this Agreement. 
 (ee) “Transfer Notice” shall mean the notice of a
proposed transfer of Shares described in Section 7. 

  
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 ACACIA COMMUNICATIONS, INC. 2009
STOCK PLAN 
 NOTICE OF STOCK OPTION
GRANT 
 (INSTALLMENT VESTING, ACCELERATION) 

The Optionee has been granted the following option to purchase shares of the Common Stock of Acacia Communications, Inc.: 

 

			
	Name of Optionee:	  	«Name»
		
	Total Number of Shares:	  	«TotalShares»
		
	Type of Option:	  	«ISO» Incentive Stock Option (ISO)
		
		  	«NSO» Nonstatutory Stock Option (NSO)
		
	Exercise Price per Share:	  	$«PricePerShare»
		
	Date of Grant:	  	«DateGrant»
		
	Date Exercisable:	  	This option may be exercised with respect to the first 25% of the Shares subject to this option when the Optionee completes 12 months of continuous Service beginning with the Vesting Commencement Date set forth below. This option
may be exercised with respect to an additional 1/48th of the Shares subject to this option when the Optionee completes each month of continuous Service thereafter. This option may become exercisable on an accelerated basis under Section 2(a) of
the Stock Option Agreement.
		
	Vesting Commencement Date:	  	«VestComDate»
		
	Expiration Date:	  	«ExpDate». This option expires earlier if the Optionee’s Service terminates earlier, as provided in Section 6 of the Stock Option Agreement.

 By signing below, the Optionee and the Company agree that this option is granted under, and governed by the terms and
conditions of, the 2009 Stock Plan and the Stock Option Agreement. Both of these documents are attached to, and made a part of, this Notice of Stock Option Grant. Section 13 of the Stock Option Agreement includes important acknowledgements
of the Optionee. 
  

							
	OPTIONEE:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

		 		 	Title:	 	  









 THE OPTION GRANTED PURSUANT TO THIS AGREEMENT AND THE SHARES ISSUABLE UPON THE EXERCISE THEREOF HAVE NOT BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH
REGISTRATION IS NOT REQUIRED. 
 ACACIA COMMUNICATIONS, INC. 2009 STOCK
PLAN: 
 STOCK OPTION AGREEMENT (INSTALLMENT
VESTING) 
 SECTION 1. GRANT OF OPTION. 

(a) Option. On the terms and conditions set forth in the Notice of Stock Option Grant and this Agreement, the Company grants to the
Optionee on the Date of Grant the option to purchase at the Exercise Price the number of Shares set forth in the Notice of Stock Option Grant. The Exercise Price is agreed to be at least 100% of the Fair Market Value per Share on the Date of Grant
(110% of Fair Market Value if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). This option is intended to be an ISO or an NSO, as provided in the Notice of Stock Option Grant. 

(b) $100,000 Limitation. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it shall be deemed to be an
NSO to the extent (and only to the extent) required by the $100,000 annual limitation under Section 422(d) of the Code. 
 (c) Stock
Plan and Defined Terms. This option is granted pursuant to the Plan, a copy of which the Optionee acknowledges having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 14 of this Agreement. 
 SECTION 2. RIGHT TO EXERCISE. 

(a) Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or part of this
option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, if the Company is subject to a Change in Control before the Optionee’s Service terminates, then at all times after
the Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service. 

(b) Stockholder Approval. Any other provision of this Agreement notwithstanding, no portion of this option shall be exercisable at any
time prior to the approval of the Plan by the Company’s stockholders. 







 SECTION 3. NO TRANSFER OR ASSIGNMENT OF OPTION. 

Except as otherwise provided in this Agreement, this option and the rights and privileges conferred hereby shall not be sold, pledged or
otherwise transferred (whether by operation of law or otherwise) and shall not be subject to sale under execution, attachment, levy or similar process. 

SECTION 4. EXERCISE PROCEDURES. 
 (a)
Notice of Exercise. The Optionee or the Optionee’s representative may exercise this option by giving written notice to the Company pursuant to Section 12(c). The notice shall specify the election to exercise this option, the number
of Shares for which it is being exercised and the form of payment. The person exercising this option shall sign the notice. In the event that this option is being exercised by the representative of the Optionee, the notice shall be accompanied by
proof (satisfactory to the Company) of the representative’s right to exercise this option. The Optionee or the Optionee’s representative shall deliver to the Company, at the time of giving the notice, payment in a form permissible under
Section 5 for the full amount of the Purchase Price. 
 (b) Issuance of Shares. After receiving a proper notice of exercise, the
Company shall cause to be issued one or more certificates evidencing the Shares for which this option has been exercised. Such Shares shall be registered (i) in the name of the person exercising this option, (ii) in the names of such
person and his or her spouse as community property or as joint tenants with the right of survivorship or (iii) with the Company’s consent, in the name of a revocable trust. The Company shall cause such certificates to be delivered to or
upon the order of the person exercising this option. 
 (c) Withholding Taxes. In the event that the Company determines that it is
required to withhold any tax as a result of the exercise of this option, the Optionee, as a condition to the exercise of this option, shall make arrangements satisfactory to the Company to enable it to satisfy all withholding requirements. The
Optionee shall also make arrangements satisfactory to the Company to enable it to satisfy any withholding requirements that may arise in connection with the disposition of Shares purchased by exercising this option. 

SECTION 5. PAYMENT FOR STOCK. 
 (a)
Cash. All or part of the Purchase Price may be paid in cash or cash equivalents. 
 (b) Surrender of Stock. At the discretion
of the Board of Directors, all or any part of the Purchase Price may be paid by surrendering, or attesting to the ownership of, Shares that are already owned by the Optionee. Such Shares shall be surrendered to the Company in good form for transfer
and shall be valued at their Fair Market Value as of the date when this option is exercised. 
 (c) Exercise/Sale. All or part of the
Purchase Price and any withholding taxes may be paid by the delivery (on a form prescribed by the Company) of an irrevocable direction to a securities broker approved by the Company to sell Shares and to deliver all or part


  
 2 








 
of the sales proceeds to the Company. However, payment pursuant to this Subsection (c) shall be permitted only if (i) Stock then is publicly traded and (ii) such payment does not
violate applicable law. 
 SECTION 6. TERM AND EXPIRATION. 

(a) Basic Term. This option shall in any event expire on the expiration date set forth in the Notice of Stock Option Grant, which date
is 10 years after the Date of Grant (five years after the Date of Grant if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). 

(b) Termination of Service (Except by Death). If the Optionee’s Service terminates for any reason other than death, then this
option shall expire on the earliest of the following occasions: 
 (i) The expiration date determined pursuant to
Subsection (a) above; 
 (ii) The date three months after the termination of the Optionee’s Service for any reason
other than Disability; or 
 (iii) The date six months after the termination of the Optionee’s Service by reason of
Disability. 
 The Optionee may exercise all or part of this option at any time before its expiration under the preceding sentence, but only to the extent
that this option had become exercisable before the Optionee’s Service terminated. When the Optionee’s Service terminates, this option shall expire immediately with respect to the number of Shares for which this option is not yet
exercisable. In the event that the Optionee dies after termination of Service but before the expiration of this option, all or part of this option may be exercised (prior to expiration) by the executors or administrators of the Optionee’s
estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s Service terminated. 

(c) Death of the Optionee. If the Optionee dies while in Service, then this option shall expire on the earlier of the following dates:

 (i) The expiration date determined pursuant to Subsection (a) above; or 

(ii) The date 12 months after the Optionee’s death. 

All or part of this option may be exercised at any time before its expiration under the preceding sentence by the executors or administrators of the
Optionee’s estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s death. When
the Optionee dies, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. 

  
 3 








 (d) Part-Time Employment and Leaves of Absence. If the Optionee commences working on a
part-time basis, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option Grant. If the Optionee goes on a leave of absence, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option
Grant in accordance with the Company’s leave of absence policy or the terms of such leave. Except as provided in the preceding sentence, Service shall be deemed to continue for any purpose under this Agreement while the Optionee is on a bona
fide leave of absence, if (i) such leave was approved by the Company in writing and (ii) continued crediting of Service for such purpose is expressly required by the terms of such leave or by applicable law (as determined by the
Company). Service shall be deemed to terminate when such leave ends, unless the Optionee immediately returns to active work. 
 (e)
Notice Concerning ISO Treatment. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it ceases to qualify for favorable tax treatment as an ISO to the extent that it is exercised: 

(i) More than three months after the date when the Optionee ceases to be an Employee for any reason other than death or
permanent and total disability (as defined in Section 22(e)(3) of the Code); 
 (ii) More than 12 months after the date
when the Optionee ceases to be an Employee by reason of permanent and total disability (as defined in Section 22(e)(3) of the Code); or 

(iii) More than three months after the date when the Optionee has been on a leave of absence for 90 days, unless the
Optionee’s reemployment rights following such leave were guaranteed by statute or by contract. 
 SECTION 7. RIGHT OF FIRST REFUSAL. 

(a) Right of First Refusal. In the event that the Optionee proposes to sell, pledge or otherwise transfer to a third party any Shares
acquired under this Agreement, or any interest in such Shares, the Company shall have the Right of First Refusal with respect to all (and not less than all) of such Shares. If the Optionee desires to transfer Shares acquired under this Agreement,
the Optionee shall give a written Transfer Notice to the Company describing fully the proposed transfer, including the number of Shares proposed to be transferred, the proposed transfer price, the name and address of the proposed Transferee and
proof satisfactory to the Company that the proposed sale or transfer will not violate any applicable federal, State or foreign securities laws. The Transfer Notice shall be signed both by the Optionee and by the proposed Transferee and must
constitute a binding commitment of both parties to the transfer of the Shares. The Company shall have the right to purchase all, and not less than all, of the Shares on the terms of the proposal described in the Transfer Notice (subject, however, to
any change in such terms permitted under Subsection (b) below) by delivery of a notice of exercise of the Right of First Refusal within 30 days after the date when the Transfer Notice was received by the Company. 

  
 4 








 (b) Transfer of Shares. If the Company fails to exercise its Right of First Refusal within
30 days after the date when it received the Transfer Notice, the Optionee may, not later than 90 days following receipt of the Transfer Notice by the Company, conclude a transfer of the Shares subject to the Transfer Notice on the terms
and conditions described in the Transfer Notice, provided that any such sale is made in compliance with applicable federal, State and foreign securities laws and not in violation of any other contractual restrictions to which the Optionee is bound.
Any proposed transfer on terms and conditions different from those described in the Transfer Notice, as well as any subsequent proposed transfer by the Optionee, shall again be subject to the Right of First Refusal and shall require compliance with
the procedure described in Subsection (a) above. If the Company exercises its Right of First Refusal, the parties shall consummate the sale of the Shares on the terms set forth in the Transfer Notice within 60 days after the date when the
Company received the Transfer Notice (or within such longer period as may have been specified in the Transfer Notice); provided, however, that in the event the Transfer Notice provided that payment for the Shares was to be made in a form other than
cash or cash equivalents paid at the time of transfer, the Company shall have the option of paying for the Shares with cash or cash equivalents equal to the present value of the consideration described in the Transfer Notice. 

(c) Additional or Exchanged Securities and Property. In the event of a merger or consolidation of the Company with or into another
entity, any other corporate reorganization, a stock split, the declaration of a stock dividend, the declaration of an extraordinary dividend payable in a form other than stock, a spin-off, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities, any securities or other property (including cash or cash equivalents) that are by reason of such transaction exchanged for, or
distributed with respect to, any Shares subject to this Section 7 shall immediately be subject to the Right of First Refusal. Appropriate adjustments to reflect the exchange or distribution of such securities or property shall be made to the
number and/or class of the Shares subject to this Section 7. 
 (d) Termination of Right of First Refusal. Any other provision
of this Section 7 notwithstanding, in the event that the Stock is readily tradable on an established securities market when the Optionee desires to transfer Shares, the Company shall have no Right of First Refusal, and the Optionee shall have
no obligation to comply with the procedures prescribed by Subsections (a) and (b) above. 
 (e) Permitted Transfers. This
Section 7 shall not apply to (i) a transfer by beneficiary designation, will or intestate succession or (ii) a transfer to one or more members of the Optionee’s Immediate Family or to a trust established by the Optionee for the
benefit of the Optionee and/or one or more members of the Optionee’s Immediate Family, provided in either case that the Transferee agrees in writing on a form prescribed by the Company to be bound by all provisions of this Agreement. If the
Optionee transfers any Shares acquired under this Agreement, either under this Subsection (e) or after the Company has failed to exercise the Right of First Refusal, then this Agreement shall apply to the Transferee to the same extent as to the
Optionee. 
 (f) Termination of Rights as Stockholder. If the Company makes available, at the time and place and in the amount and
form provided in this Agreement, the consideration 

  
 5 








 
for the Shares to be purchased in accordance with this Section 7, then after such time the person from whom such Shares are to be purchased shall no longer have any rights as a holder of
such Shares (other than the right to receive payment of such consideration in accordance with this Agreement). Such Shares shall be deemed to have been purchased in accordance with the applicable provisions hereof, whether or not the certificate(s)
therefor have been delivered as required by this Agreement. 
 (g) Assignment of Right of First Refusal. The Board of Directors may
freely assign the Company’s Right of First Refusal, in whole or in part. Any person who accepts an assignment of the Right of First Refusal from the Company shall assume all of the Company’s rights and obligations under this
Section 7. 
 SECTION 8. LEGALITY OF INITIAL ISSUANCE. 

No Shares shall be issued upon the exercise of this option unless and until the Company has determined that: 

(a) It and the Optionee have taken any actions required to register the Shares under the Securities Act or to perfect an
exemption from the registration requirements thereof; 
 (b) Any applicable listing requirement of any stock exchange or
other securities market on which Stock is listed has been satisfied; and 
 (c) Any other applicable provision of federal,
State or foreign law has been satisfied. 
 SECTION 9. NO REGISTRATION RIGHTS. 

The Company may, but shall not be obligated to, register or qualify the sale of Shares under the Securities Act or any other applicable law.
The Company shall not be obligated to take any affirmative action in order to cause the sale of Shares under this Agreement to comply with any law. 

SECTION 10. RESTRICTIONS ON TRANSFER OF SHARES. 

(a) Securities Law Restrictions. Regardless of whether the offering and sale of Shares under the Plan have been registered under the
Securities Act or have been registered or qualified under the securities laws of any State, the Company at its discretion may impose restrictions upon the sale, pledge or other transfer of such Shares (including the placement of appropriate legends
on stock certificates or the imposition of stop-transfer instructions) if, in the judgment of the Company, such restrictions are necessary or desirable in order to achieve compliance with the Securities Act,
the securities laws of any State or any other law. 
 (b) Market Stand-Off. In connection with any underwritten public offering by
the Company of its equity securities pursuant to an effective registration statement filed under the Securities Act, including the Company’s initial public offering, the Optionee or a Transferee shall not directly or indirectly sell, make any
short sale of, loan, hypothecate, pledge, offer, grant 

  
 6 








 
or sell any option or other contract for the purchase of, purchase any option or other contract for the sale of, or otherwise dispose of or transfer, or agree to engage in any of the foregoing
transactions with respect to, any Shares acquired under this Agreement without the prior written consent of the Company or its managing underwriter. Such restriction (the “Market Stand-Off”) shall be in effect for such period of time
following the date of the final prospectus for the offering as may be requested by the Company or such underwriter. In no event, however, shall such period exceed 180 days plus such additional period as may reasonably be requested by the Company or
such underwriter to accommodate regulatory restrictions on (i) the publication or other distribution of research reports or (ii) analyst recommendations and opinions, including (without limitation) the restrictions set forth in
Rule 2711(f)(4) of the National Association of Securities Dealers and Rule 472(f)(4) of the New York Stock Exchange, as amended, or any similar successor rules. The Market Stand-Off shall in any event terminate two years after the date of
the Company’s initial public offering. In the event of the declaration of a stock dividend, a spin-off, a stock split, an adjustment in conversion ratio, a recapitalization or a similar transaction
affecting the Company’s outstanding securities without receipt of consideration, any new, substituted or additional securities which are by reason of such transaction distributed with respect to any Shares subject to the Market Stand-Off, or
into which such Shares thereby become convertible, shall immediately be subject to the Market Stand-Off. In order to enforce the Market Stand-Off, the Company may impose stop-transfer instructions with respect to the Shares acquired under this
Agreement until the end of the applicable stand-off period. The Company’s underwriters shall be beneficiaries of the agreement set forth in this Subsection (b). This Subsection (b) shall not apply to Shares registered in the public
offering under the Securities Act. 
 (c) Investment Intent at Grant. The Optionee represents and agrees that the Shares to be
acquired upon exercising this option will be acquired for investment, and not with a view to the sale or distribution thereof. 
 (d)
Investment Intent at Exercise. In the event that the sale of Shares under the Plan is not registered under the Securities Act but an exemption is available that requires an investment representation or other representation, the Optionee shall
represent and agree at the time of exercise that the Shares being acquired upon exercising this option are being acquired for investment, and not with a view to the sale or distribution thereof, and shall make such other representations as are
deemed necessary or appropriate by the Company and its counsel. 
 (e) Legends. All certificates evidencing Shares purchased under
this Agreement shall bear the following legend: 
 “THE SHARES REPRESENTED HEREBY MAY NOT BE SOLD, ASSIGNED, TRANSFERRED, ENCUMBERED OR
IN ANY MANNER DISPOSED OF, EXCEPT IN COMPLIANCE WITH THE TERMS OF A WRITTEN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER OF THE SHARES (OR THE PREDECESSOR IN INTEREST TO THE SHARES). SUCH AGREEMENT GRANTS TO THE COMPANY CERTAIN RIGHTS OF
FIRST REFUSAL UPON AN ATTEMPTED TRANSFER OF THE SHARES. THE SECRETARY OF THE COMPANY WILL UPON WRITTEN REQUEST FURNISH A COPY OF SUCH AGREEMENT TO THE HOLDER HEREOF WITHOUT CHARGE.” 

  
 7 








 All certificates evidencing Shares purchased under this Agreement in an unregistered transaction shall bear the
following legend (and such other restrictive legends as are required or deemed advisable under the provisions of any applicable law): 

“THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR
OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.” 

(f) Removal of Legends. If, in the opinion of the Company and its counsel, any legend placed on a stock certificate representing Shares
sold under this Agreement is no longer required, the holder of such certificate shall be entitled to exchange such certificate for a certificate representing the same number of Shares but without such legend. 

(g) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth in this
Section 10 shall be conclusive and binding on the Optionee and all other persons. 
 SECTION 11. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 8(a) of the Plan, the terms of this option (including, without limitation, the number
and kind of Shares subject to this option and the Exercise Price) shall be adjusted as set forth in Section 8(a) of the Plan. In the event that the Company is a party to a merger or consolidation, this option shall be subject to the agreement
of merger or consolidation, as provided in Section 8(b) of the Plan. 
 SECTION 12. MISCELLANEOUS PROVISIONS. 

(a) Rights as a Stockholder. Neither the Optionee nor the Optionee’s representative shall have any rights as a stockholder with
respect to any Shares subject to this option until the Optionee or the Optionee’s representative becomes entitled to receive such Shares by filing a notice of exercise and paying the Purchase Price pursuant to Sections 4 and 5. 

(b) No Retention Rights. Nothing in this option or in the Plan shall confer upon the Optionee any right to continue in Service for any
period of specific duration or interfere with or otherwise restrict in any way the rights of the Company (or any Parent or Subsidiary employing or retaining the Optionee) or of the Optionee, which rights are hereby expressly reserved by each, to
terminate his or her Service at any time and for any reason, with or without cause. 
 (c) Notice. Any notice required by the terms
of this Agreement shall be given in writing. It shall be deemed effective upon (i) personal delivery, (ii) deposit with the United States Postal Service, by registered or certified mail, with postage and fees prepaid or (iii) deposit
with Federal Express Corporation, with shipping charges prepaid. Notice shall be addressed to the Company at its principal executive office and to the Optionee at the address that he or she most recently provided to the Company in accordance with
this Subsection (c). 

  
 8 








 (d) Modifications and Waivers. No provision of this Agreement shall be modified, waived or
discharged unless the modification, waiver or discharge is agreed to in writing and signed by the Optionee and by an authorized officer of the Company (other than the Optionee). No waiver by either party of any breach of, or of compliance with, any
condition or provision of this Agreement by the other party shall be considered a waiver of any other condition or provision or of the same condition or provision at another time. 

(e) Entire Agreement. The Notice of Stock Option Grant, this Agreement and the Plan constitute the entire contract between the parties
hereto with regard to the subject matter hereof. They supersede any other agreements, representations or understandings (whether oral or written and whether express or implied) that relate to the subject matter hereof. 

(f) Choice of Law. This Agreement shall be governed by, and construed in accordance with, the laws of the State of Delaware, as such
laws are applied to contracts entered into and performed in such State. 
 SECTION 13. ACKNOWLEDGEMENTS OF THE OPTIONEE. 

(a) Tax Consequences. The Optionee agrees that the Company does not have a duty to design or administer the Plan or its other
compensation programs in a manner that minimizes the Optionee’s tax liabilities. The Optionee shall not make any claim against the Company or its Board of Directors, officers or employees related to tax liabilities arising from this option or
the Optionee’s other compensation. In particular, the Optionee acknowledges that this option is exempt from Section 409A of the Code only if the Exercise Price is at least equal to the Fair Market Value per Share on the Date of Grant.
Since Shares are not traded on an established securities market, the determination of their Fair Market Value is made by the Board of Directors or by an independent valuation firm retained by the Company. The Optionee acknowledges that there is no
guarantee in either case that the Internal Revenue Service will agree with the valuation, and the Optionee shall not make any claim against the Company or its Board of Directors, officers or employees in the event that the Internal Revenue Service
asserts that the valuation was too low. 
 (b) Electronic Delivery of Documents. The Optionee agrees to accept by email all documents
relating to the Company, the Plan or this option and all other documents that the Company is required to deliver to its security holders (including, without limitation, disclosures that may be required by the Securities and Exchange Commission). The
Optionee also agrees that the Company may deliver these documents by posting them on a website maintained by the Company or by a third party under contract with the Company. If the Company posts these documents on a website, it shall notify the
Optionee by email of their availability. The Optionee acknowledges that he or she may incur costs in connection with electronic delivery, including the cost of accessing the internet and printing fees, and that an interruption of internet access may
interfere with his or her ability to access the documents. This consent shall remain in effect until this option expires or until the Optionee gives the Company written notice that it should deliver paper documents. 

(c) No Notice of Expiration Date. The Optionee agrees that the Company and its officers, employees, attorneys and agents do not have
any obligation to notify him or her 

  
 9 








 
prior to the expiration of this option pursuant to Section 6, regardless of whether this option will expire at the end of its full term or on an earlier date related to the termination of
the Optionee’s Service. The Optionee further agrees that he or she has the sole responsibility for monitoring the expiration of this option and for exercising this option, if at all, before it expires. This Subsection (c) shall supersede
any contrary representation that may have been made, orally or in writing, by the Company or by an officer, employee, attorney or agent of the Company. 

SECTION 14. DEFINITIONS. 
 (a)
“Agreement” shall mean this Stock Option Agreement. 
 (b) “Board of Directors” shall mean the Board of
Directors of the Company, as constituted from time to time or, if a Committee has been appointed, such Committee. 
 (c)
“Cause” shall mean a good faith determination by the Board of Directors of any of the following: 
 (i) An
unauthorized use or disclosure by the Optionee of the Company’s confidential information or trade secrets, which use or disclosure causes material harm to the Company; 

(ii) A material breach by the Optionee of any material agreement between the Purchaser and the Company; 

(iii) A material failure by the Optionee to comply with the Company’s written policies or rules after receiving written
notification of such failure from the Board of Directors; 
 (iv) The Optionee’s conviction of, or plea of
“guilty” or “no contest” to, a felony under the laws of the United States or any state thereof; 
 (v)
The Optionee’s gross negligence or willful misconduct in the course of performing Service; 
 (vi) A continuing failure
by the Optionee to perform reasonably assigned duties after receiving written notification of such failure from the Board of Directors; or 

(vii) A failure by the Optionee to cooperate in good faith with a governmental or internal investigation of the Company or its
directors, officers or employees, if the Company has requested the Purchaser’s cooperation 
 (d) “Change in Control”
shall mean (i) the consummation of a merger or consolidation of the Company with or into another entity or (ii) the sale, transfer or other disposition of all or substantially all of the Company’s assets. The foregoing
notwithstanding, a merger or consolidation of the Company shall not constitute a “Change in Control” if immediately after such merger or consolidation a majority of the voting power of the capital stock of the continuing or surviving
entity, or any direct or indirect parent corporation of such 

  
 10 








 
continuing or surviving entity, will be owned by persons who were the Company’s stockholders immediately prior to such merger or consolidation in substantially the same proportions as their
ownership of the voting power of the Company’s capital stock immediately prior to such merger or consolidation. 
 (e)
“Code” shall mean the Internal Revenue Code of 1986, as amended. 
 (f) “Committee” shall mean a committee
of the Board of Directors, as described in Section 2 of the Plan. 
 (g) “Company” shall mean Acacia Communications,
Inc., a Delaware corporation. 
 (h) “Consultant” shall mean a person who performs bona fide services for the Company, a
Parent or a Subsidiary as a consultant or advisor, excluding Employees and Outside Directors. 
 (i) “Date of Grant” shall
mean the date of grant specified in the Notice of Stock Option Grant, which date shall be the later of (i) the date on which the Board of Directors resolved to grant this option or (ii) the first day of the Optionee’s Service. 

(j) “Disability” shall mean that the Optionee is unable to engage in any substantial gainful activity by reason of any
medically determinable physical or mental impairment. 
 (k) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (l) “Exercise Price”
shall mean the amount for which one Share may be purchased upon exercise of this option, as specified in the Notice of Stock Option Grant. 

(m) “Fair Market Value” shall mean the fair market value of a Share, as determined by the Board of Directors in good faith.
Such determination shall be conclusive and binding on all persons. 
 (n) “Immediate Family” shall mean any child,
stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling, mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law or sister-in-law and shall include adoptive relationships. 

(o) “Involuntary Termination” shall mean the termination of the Optionee’s Service by reason of: 

(i) The involuntary discharge of the Optionee by the Company (or the Parent or Subsidiary employing him) for reasons other than
Cause; or 
 (ii) The voluntary resignation of the Optionee following any of the following events, if such event occurs
without the consent of the Optionee: (A) a change in the Optionee’s position with the Company (or the Parent or 

  
 11 








 
Subsidiary employing him or her) that materially reduces his or her level of authority or responsibility (provided that the Optionee’s level of authority or responsibility shall not be
deemed to be reduced merely because there are additional employees more senior to the Optionee as a result of the Change in Control), (B) a reduction in the Optionee’s base salary by more than 10%, unless such reduction is made in
connection with a commensurate reduction in the compensation of employees of the Company generally, or (C) receipt of notice that the Optionee’s principal workplace will be relocated more than 50 miles 

(p) “ISO” shall mean an employee incentive stock option described in Section 422(b) of the Code. 

(q) “Notice of Stock Option Grant” shall mean the document so entitled to which this Agreement is attached. 

(r) “NSO” shall mean a stock option not described in Section 422(b) or 423(b) of the Code. 

(s) “Optionee” shall mean the person named in the Notice of Stock Option Grant. 

(t) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(u) “Parent” shall mean any corporation (other than the Company) in an unbroken chain of corporations ending with the
Company, if each of the corporations other than the Company owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. 

(v) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as in effect on the Date of Grant. 

(w) “Purchase Price” shall mean the Exercise Price multiplied by the number of Shares with respect to which this option is
being exercised. 
 (x) “Right of First Refusal” shall mean the Company’s right of first refusal described in
Section 7. 
 (y) “Securities Act” shall mean the Securities Act of 1933, as amended. 

(z) “Service” shall mean service as an Employee, Outside Director or Consultant. 

(aa) “Share” shall mean one share of Stock, as adjusted in accordance with Section 8 of the Plan (if applicable). 

(bb) “Stock” shall mean the Common Stock of the Company. 

  
 12 








 (cc) “Subsidiary” shall mean any corporation (other than the Company) in an
unbroken chain of corporations beginning with the Company, if each of the corporations other than the last corporation in the unbroken chain owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the
other corporations in such chain. 
 (dd) “Transferee” shall mean any person to whom the Optionee has directly or
indirectly transferred any Share acquired under this Agreement. 
 (ee) “Transfer Notice” shall mean the notice of a
proposed transfer of Shares described in Section 7. 

  
 13 








 ACACIA COMMUNICATIONS, INC. 2009
STOCK PLAN 
 NOTICE OF STOCK OPTION
GRANT 
 (INSTALLMENT VESTING, ACCELERATION) 

The Optionee has been granted the following option to purchase shares of the Common Stock of Acacia Communications, Inc.: 

 

			
	Name of Optionee:	  	«Name»
		
	Total Number of Shares:	  	«TotalShares»
		
	Type of Option:	  	«ISO» Incentive Stock Option (ISO)
		
		  	«NSO» Nonstatutory Stock Option (NSO)
		
	Exercise Price per Share:	  	$«PricePerShare»
		
	Date of Grant:	  	«DateGrant»
		
	Date Exercisable:	  	This option may be exercised with respect to the first 25% of the Shares subject to this option when the Optionee completes 12 months of continuous Service beginning with the Vesting Commencement Date set forth below. This option
may be exercised with respect to an additional 1/48th of the Shares subject to this option when the Optionee completes each month of continuous Service thereafter. This option may become exercisable on an accelerated basis under Section 2(a) of
the Stock Option Agreement.
		
	Vesting Commencement Date:	  	«VestComDate»
		
	Expiration Date:	  	«ExpDate». This option expires earlier if the Optionee’s Service terminates earlier, as provided in Section 6 of the Stock Option Agreement.

 By signing below, the Optionee and the Company agree that this option is granted under, and governed by the terms and
conditions of, the 2009 Stock Plan and the Stock Option Agreement. Both of these documents are attached to, and made a part of, this Notice of Stock Option Grant. Section 13 of the Stock Option Agreement includes important acknowledgements
of the Optionee. 
  

							
	OPTIONEE:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

		 		 	Title:	 	  









 THE OPTION GRANTED PURSUANT TO THIS AGREEMENT AND THE SHARES ISSUABLE UPON THE EXERCISE THEREOF HAVE NOT BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH
REGISTRATION IS NOT REQUIRED. 
 ACACIA COMMUNICATIONS, INC. 2009 STOCK
PLAN: 
 STOCK OPTION AGREEMENT (INSTALLMENT
VESTING) 
 SECTION 1. GRANT OF OPTION. 

(a) Option. On the terms and conditions set forth in the Notice of Stock Option Grant and this Agreement, the Company grants to the
Optionee on the Date of Grant the option to purchase at the Exercise Price the number of Shares set forth in the Notice of Stock Option Grant. The Exercise Price is agreed to be at least 100% of the Fair Market Value per Share on the Date of Grant
(110% of Fair Market Value if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). This option is intended to be an ISO or an NSO, as provided in the Notice of Stock Option Grant. 

(b) $100,000 Limitation. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it shall be deemed to be an
NSO to the extent (and only to the extent) required by the $100,000 annual limitation under Section 422(d) of the Code. 
 (c) Stock
Plan and Defined Terms. This option is granted pursuant to the Plan, a copy of which the Optionee acknowledges having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 14 of this Agreement. 
 SECTION 2. RIGHT TO EXERCISE. 

(a) Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or part of this
option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, the following rules shall apply if the Company is subject to a Change in Control before the Optionee’s Service
terminates: 
  

	 	i.	At all times after the Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service. 









	 	ii.	If the Optionee is subject to an Involuntary Termination upon or after the Change in Control, then this option shall vest in full and become immediately exercisable. 


(b) Stockholder Approval. Any other provision of this Agreement notwithstanding, no portion of this option shall be exercisable at any
time prior to the approval of the Plan by the Company’s stockholders. 
 SECTION 3. NO TRANSFER OR ASSIGNMENT OF OPTION. 

Except as otherwise provided in this Agreement, this option and the rights and privileges conferred hereby shall not be sold, pledged or
otherwise transferred (whether by operation of law or otherwise) and shall not be subject to sale under execution, attachment, levy or similar process. 

SECTION 4. EXERCISE PROCEDURES. 
 (a)
Notice of Exercise. The Optionee or the Optionee’s representative may exercise this option by giving written notice to the Company pursuant to Section 12(c). The notice shall specify the election to exercise this option, the number
of Shares for which it is being exercised and the form of payment. The person exercising this option shall sign the notice. In the event that this option is being exercised by the representative of the Optionee, the notice shall be accompanied by
proof (satisfactory to the Company) of the representative’s right to exercise this option. The Optionee or the Optionee’s representative shall deliver to the Company, at the time of giving the notice, payment in a form permissible under
Section 5 for the full amount of the Purchase Price. 
 (b) Issuance of Shares. After receiving a proper notice of exercise, the
Company shall cause to be issued one or more certificates evidencing the Shares for which this option has been exercised. Such Shares shall be registered (i) in the name of the person exercising this option, (ii) in the names of such
person and his or her spouse as community property or as joint tenants with the right of survivorship or (iii) with the Company’s consent, in the name of a revocable trust. The Company shall cause such certificates to be delivered to or
upon the order of the person exercising this option. 
 (c) Withholding Taxes. In the event that the Company determines that it is
required to withhold any tax as a result of the exercise of this option, the Optionee, as a condition to the exercise of this option, shall make arrangements satisfactory to the Company to enable it to satisfy all withholding requirements. The
Optionee shall also make arrangements satisfactory to the Company to enable it to satisfy any withholding requirements that may arise in connection with the disposition of Shares purchased by exercising this option. 

SECTION 5. PAYMENT FOR STOCK. 
 (a)
Cash. All or part of the Purchase Price may be paid in cash or cash equivalents. 

  
 2 








 (b) Surrender of Stock. At the discretion of the Board of Directors, all or any part of
the Purchase Price may be paid by surrendering, or attesting to the ownership of, Shares that are already owned by the Optionee. Such Shares shall be surrendered to the Company in good form for transfer and shall be valued at their Fair Market Value
as of the date when this option is exercised. 
 (c) Exercise/Sale. All or part of the Purchase Price and any withholding taxes may
be paid by the delivery (on a form prescribed by the Company) of an irrevocable direction to a securities broker approved by the Company to sell Shares and to deliver all or part of the sales proceeds to the Company. However, payment pursuant to
this Subsection (c) shall be permitted only if (i) Stock then is publicly traded and (ii) such payment does not violate applicable law. 

SECTION 6. TERM AND EXPIRATION. 
 (a)
Basic Term. This option shall in any event expire on the expiration date set forth in the Notice of Stock Option Grant, which date is 10 years after the Date of Grant (five years after the Date of Grant if this option is designated as an ISO
in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). 
 (b) Termination of Service (Except by Death). If
the Optionee’s Service terminates for any reason other than death, then this option shall expire on the earliest of the following occasions: 

(i) The expiration date determined pursuant to Subsection (a) above; 

(ii) The date three months after the termination of the Optionee’s Service for any reason other than Disability; or 

(iii) The date six months after the termination of the Optionee’s Service by reason of Disability. 

The Optionee may exercise all or part of this option at any time before its expiration under the preceding sentence, but only to the extent that this option
had become exercisable before the Optionee’s Service terminated. When the Optionee’s Service terminates, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. In the event
that the Optionee dies after termination of Service but before the expiration of this option, all or part of this option may be exercised (prior to expiration) by the executors or administrators of the Optionee’s estate or by any person who has
acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s Service terminated. 

(c) Death of the Optionee. If the Optionee dies while in Service, then this option shall expire on the earlier of the following dates:

 (i) The expiration date determined pursuant to Subsection (a) above; or 

  
 3 








 (ii) The date 12 months after the Optionee’s death. 

All or part of this option may be exercised at any time before its expiration under the preceding sentence by the executors or administrators of the
Optionee’s estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s death. When
the Optionee dies, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. 

(d) Part-Time Employment and Leaves of Absence. If the Optionee commences working on a part-time basis, then the Company may adjust the
vesting schedule set forth in the Notice of Stock Option Grant. If the Optionee goes on a leave of absence, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option Grant in accordance with the Company’s leave of
absence policy or the terms of such leave. Except as provided in the preceding sentence, Service shall be deemed to continue for any purpose under this Agreement while the Optionee is on a bona fide leave of absence, if (i) such leave
was approved by the Company in writing and (ii) continued crediting of Service for such purpose is expressly required by the terms of such leave or by applicable law (as determined by the Company). Service shall be deemed to terminate when such
leave ends, unless the Optionee immediately returns to active work. 
 (e) Notice Concerning ISO Treatment. Even if this option is
designated as an ISO in the Notice of Stock Option Grant, it ceases to qualify for favorable tax treatment as an ISO to the extent that it is exercised: 

(i) More than three months after the date when the Optionee ceases to be an Employee for any reason other than death or
permanent and total disability (as defined in Section 22(e)(3) of the Code); 
 (ii) More than 12 months after the date
when the Optionee ceases to be an Employee by reason of permanent and total disability (as defined in Section 22(e)(3) of the Code); or 

(iii) More than three months after the date when the Optionee has been on a leave of absence for 90 days, unless the
Optionee’s reemployment rights following such leave were guaranteed by statute or by contract. 
 SECTION 7. RIGHT OF FIRST REFUSAL. 

(a) Right of First Refusal. In the event that the Optionee proposes to sell, pledge or otherwise transfer to a third party any Shares
acquired under this Agreement, or any interest in such Shares, the Company shall have the Right of First Refusal with respect to all (and not less than all) of such Shares. If the Optionee desires to transfer Shares acquired under this Agreement,
the Optionee shall give a written Transfer Notice to the Company describing fully the proposed transfer, including the number of Shares proposed to be transferred, the proposed transfer price, the name and address of the proposed Transferee and
proof satisfactory to the Company that the proposed sale or transfer will not violate any applicable federal, State or foreign securities laws. The Transfer Notice shall be signed both by the Optionee and by the


  
 4 








 
proposed Transferee and must constitute a binding commitment of both parties to the transfer of the Shares. The Company shall have the right to purchase all, and not less than all, of the Shares
on the terms of the proposal described in the Transfer Notice (subject, however, to any change in such terms permitted under Subsection (b) below) by delivery of a notice of exercise of the Right of First Refusal within 30 days after the date
when the Transfer Notice was received by the Company. 
 (b) Transfer of Shares. If the Company fails to exercise its Right of First
Refusal within 30 days after the date when it received the Transfer Notice, the Optionee may, not later than 90 days following receipt of the Transfer Notice by the Company, conclude a transfer of the Shares subject to the Transfer Notice
on the terms and conditions described in the Transfer Notice, provided that any such sale is made in compliance with applicable federal, State and foreign securities laws and not in violation of any other contractual restrictions to which the
Optionee is bound. Any proposed transfer on terms and conditions different from those described in the Transfer Notice, as well as any subsequent proposed transfer by the Optionee, shall again be subject to the Right of First Refusal and shall
require compliance with the procedure described in Subsection (a) above. If the Company exercises its Right of First Refusal, the parties shall consummate the sale of the Shares on the terms set forth in the Transfer Notice within 60 days
after the date when the Company received the Transfer Notice (or within such longer period as may have been specified in the Transfer Notice); provided, however, that in the event the Transfer Notice provided that payment for the Shares was to be
made in a form other than cash or cash equivalents paid at the time of transfer, the Company shall have the option of paying for the Shares with cash or cash equivalents equal to the present value of the consideration described in the Transfer
Notice. 
 (c) Additional or Exchanged Securities and Property. In the event of a merger or consolidation of the Company with or into
another entity, any other corporate reorganization, a stock split, the declaration of a stock dividend, the declaration of an extraordinary dividend payable in a form other than stock, a spin-off, an
adjustment in conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities, any securities or other property (including cash or cash equivalents) that are by reason of such transaction exchanged
for, or distributed with respect to, any Shares subject to this Section 7 shall immediately be subject to the Right of First Refusal. Appropriate adjustments to reflect the exchange or distribution of such securities or property shall be made
to the number and/or class of the Shares subject to this Section 7. 
 (d) Termination of Right of First Refusal. Any other
provision of this Section 7 notwithstanding, in the event that the Stock is readily tradable on an established securities market when the Optionee desires to transfer Shares, the Company shall have no Right of First Refusal, and the Optionee
shall have no obligation to comply with the procedures prescribed by Subsections (a) and (b) above. 
 (e) Permitted
Transfers. This Section 7 shall not apply to (i) a transfer by beneficiary designation, will or intestate succession or (ii) a transfer to one or more members of the Optionee’s Immediate Family or to a trust established by
the Optionee for the benefit of the Optionee and/or one or more members of the Optionee’s Immediate Family, provided in either case that the Transferee agrees in writing on a form prescribed by the Company to be bound by


  
 5 








 
all provisions of this Agreement. If the Optionee transfers any Shares acquired under this Agreement, either under this Subsection (e) or after the Company has failed to exercise the Right
of First Refusal, then this Agreement shall apply to the Transferee to the same extent as to the Optionee. 
 (f) Termination of Rights
as Stockholder. If the Company makes available, at the time and place and in the amount and form provided in this Agreement, the consideration for the Shares to be purchased in accordance with this Section 7, then after such time the person
from whom such Shares are to be purchased shall no longer have any rights as a holder of such Shares (other than the right to receive payment of such consideration in accordance with this Agreement). Such Shares shall be deemed to have been
purchased in accordance with the applicable provisions hereof, whether or not the certificate(s) therefor have been delivered as required by this Agreement. 

(g) Assignment of Right of First Refusal. The Board of Directors may freely assign the Company’s Right of First Refusal, in whole
or in part. Any person who accepts an assignment of the Right of First Refusal from the Company shall assume all of the Company’s rights and obligations under this Section 7. 

SECTION 8. LEGALITY OF INITIAL ISSUANCE. 

No Shares shall be issued upon the exercise of this option unless and until the Company has determined that: 

(a) It and the Optionee have taken any actions required to register the Shares under the Securities Act or to perfect an
exemption from the registration requirements thereof; 
 (b) Any applicable listing requirement of any stock exchange or
other securities market on which Stock is listed has been satisfied; and 
 (c) Any other applicable provision of federal,
State or foreign law has been satisfied. 
 SECTION 9. NO REGISTRATION RIGHTS. 

The Company may, but shall not be obligated to, register or qualify the sale of Shares under the Securities Act or any other applicable law.
The Company shall not be obligated to take any affirmative action in order to cause the sale of Shares under this Agreement to comply with any law. 

SECTION 10. RESTRICTIONS ON TRANSFER OF SHARES. 

(a) Securities Law Restrictions. Regardless of whether the offering and sale of Shares under the Plan have been registered under the
Securities Act or have been registered or qualified under the securities laws of any State, the Company at its discretion may impose restrictions upon the sale, pledge or other transfer of such Shares (including the placement of appropriate legends
on stock certificates or the imposition of stop-transfer instructions) if, in the judgment of the Company, such restrictions are necessary or desirable in order to achieve compliance with the Securities Act,
the securities laws of any State or any other law. 

  
 6 








 (b) Market Stand-Off. In connection with any underwritten public offering by the Company
of its equity securities pursuant to an effective registration statement filed under the Securities Act, including the Company’s initial public offering, the Optionee or a Transferee shall not directly or indirectly sell, make any short sale
of, loan, hypothecate, pledge, offer, grant or sell any option or other contract for the purchase of, purchase any option or other contract for the sale of, or otherwise dispose of or transfer, or agree to engage in any of the foregoing transactions
with respect to, any Shares acquired under this Agreement without the prior written consent of the Company or its managing underwriter. Such restriction (the “Market Stand-Off”) shall be in effect for such period of time following the date
of the final prospectus for the offering as may be requested by the Company or such underwriter. In no event, however, shall such period exceed 180 days plus such additional period as may reasonably be requested by the Company or such underwriter to
accommodate regulatory restrictions on (i) the publication or other distribution of research reports or (ii) analyst recommendations and opinions, including (without limitation) the restrictions set forth in Rule 2711(f)(4) of the
National Association of Securities Dealers and Rule 472(f)(4) of the New York Stock Exchange, as amended, or any similar successor rules. The Market Stand-Off shall in any event terminate two years after the date of the Company’s initial
public offering. In the event of the declaration of a stock dividend, a spin-off, a stock split, an adjustment in conversion ratio, a recapitalization or a similar transaction affecting the Company’s
outstanding securities without receipt of consideration, any new, substituted or additional securities which are by reason of such transaction distributed with respect to any Shares subject to the Market Stand-Off, or into which such Shares thereby
become convertible, shall immediately be subject to the Market Stand-Off. In order to enforce the Market Stand-Off, the Company may impose stop-transfer instructions with respect to the Shares acquired under this Agreement until the end of the
applicable stand-off period. The Company’s underwriters shall be beneficiaries of the agreement set forth in this Subsection (b). This Subsection (b) shall not apply to Shares registered in the public offering under the Securities
Act. 
 (c) Investment Intent at Grant. The Optionee represents and agrees that the Shares to be acquired upon exercising this option
will be acquired for investment, and not with a view to the sale or distribution thereof. 
 (d) Investment Intent at Exercise. In
the event that the sale of Shares under the Plan is not registered under the Securities Act but an exemption is available that requires an investment representation or other representation, the Optionee shall represent and agree at the time of
exercise that the Shares being acquired upon exercising this option are being acquired for investment, and not with a view to the sale or distribution thereof, and shall make such other representations as are deemed necessary or appropriate by the
Company and its counsel. 
 (e) Legends. All certificates evidencing Shares purchased under this Agreement shall bear the following
legend: 
 “THE SHARES REPRESENTED HEREBY MAY NOT BE SOLD, ASSIGNED, TRANSFERRED, ENCUMBERED OR IN ANY MANNER DISPOSED OF, EXCEPT IN
COMPLIANCE WITH THE TERMS OF A WRITTEN 

  
 7 








 
AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER OF THE SHARES (OR THE PREDECESSOR IN INTEREST TO THE SHARES). SUCH AGREEMENT GRANTS TO THE COMPANY CERTAIN RIGHTS OF FIRST REFUSAL UPON AN
ATTEMPTED TRANSFER OF THE SHARES. THE SECRETARY OF THE COMPANY WILL UPON WRITTEN REQUEST FURNISH A COPY OF SUCH AGREEMENT TO THE HOLDER HEREOF WITHOUT CHARGE.” 

All certificates evidencing Shares purchased under this Agreement in an unregistered transaction shall bear the following legend (and such other restrictive
legends as are required or deemed advisable under the provisions of any applicable law): 
 “THE SHARES REPRESENTED HEREBY HAVE NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT
SUCH REGISTRATION IS NOT REQUIRED.” 
 (f) Removal of Legends. If, in the opinion of the Company and its counsel, any legend
placed on a stock certificate representing Shares sold under this Agreement is no longer required, the holder of such certificate shall be entitled to exchange such certificate for a certificate representing the same number of Shares but without
such legend. 
 (g) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth
in this Section 10 shall be conclusive and binding on the Optionee and all other persons. 
 SECTION 11. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 8(a) of the Plan, the terms of this option (including, without limitation, the number
and kind of Shares subject to this option and the Exercise Price) shall be adjusted as set forth in Section 8(a) of the Plan. In the event that the Company is a party to a merger or consolidation, this option shall be subject to the agreement
of merger or consolidation, as provided in Section 8(b) of the Plan. 
 SECTION 12. MISCELLANEOUS PROVISIONS. 

(a) Rights as a Stockholder. Neither the Optionee nor the Optionee’s representative shall have any rights as a stockholder with
respect to any Shares subject to this option until the Optionee or the Optionee’s representative becomes entitled to receive such Shares by filing a notice of exercise and paying the Purchase Price pursuant to Sections 4 and 5. 

(b) No Retention Rights. Nothing in this option or in the Plan shall confer upon the Optionee any right to continue in Service for any
period of specific duration or interfere with or otherwise restrict in any way the rights of the Company (or any Parent or Subsidiary employing or retaining the Optionee) or of the Optionee, which rights are hereby expressly reserved by each, to
terminate his or her Service at any time and for any reason, with or without cause. 

  
 8 








 (c) Notice. Any notice required by the terms of this Agreement shall be given in writing.
It shall be deemed effective upon (i) personal delivery, (ii) deposit with the United States Postal Service, by registered or certified mail, with postage and fees prepaid or (iii) deposit with Federal Express Corporation, with
shipping charges prepaid. Notice shall be addressed to the Company at its principal executive office and to the Optionee at the address that he or she most recently provided to the Company in accordance with this Subsection (c). 

(d) Modifications and Waivers. No provision of this Agreement shall be modified, waived or discharged unless the modification, waiver
or discharge is agreed to in writing and signed by the Optionee and by an authorized officer of the Company (other than the Optionee). No waiver by either party of any breach of, or of compliance with, any condition or provision of this Agreement by
the other party shall be considered a waiver of any other condition or provision or of the same condition or provision at another time. 

(e) Entire Agreement. The Notice of Stock Option Grant, this Agreement and the Plan constitute the entire contract between the parties
hereto with regard to the subject matter hereof. They supersede any other agreements, representations or understandings (whether oral or written and whether express or implied) that relate to the subject matter hereof. 

(f) Choice of Law. This Agreement shall be governed by, and construed in accordance with, the laws of the State of Delaware, as such
laws are applied to contracts entered into and performed in such State. 
 SECTION 13. ACKNOWLEDGEMENTS OF THE OPTIONEE. 

(a) Tax Consequences. The Optionee agrees that the Company does not have a duty to design or administer the Plan or its other
compensation programs in a manner that minimizes the Optionee’s tax liabilities. The Optionee shall not make any claim against the Company or its Board of Directors, officers or employees related to tax liabilities arising from this option or
the Optionee’s other compensation. In particular, the Optionee acknowledges that this option is exempt from Section 409A of the Code only if the Exercise Price is at least equal to the Fair Market Value per Share on the Date of Grant.
Since Shares are not traded on an established securities market, the determination of their Fair Market Value is made by the Board of Directors or by an independent valuation firm retained by the Company. The Optionee acknowledges that there is no
guarantee in either case that the Internal Revenue Service will agree with the valuation, and the Optionee shall not make any claim against the Company or its Board of Directors, officers or employees in the event that the Internal Revenue Service
asserts that the valuation was too low. 
 (b) Electronic Delivery of Documents. The Optionee agrees to accept by email all documents
relating to the Company, the Plan or this option and all other documents that the Company is required to deliver to its security holders (including, without limitation, disclosures that may be required by the Securities and Exchange Commission). The
Optionee also agrees that the Company may deliver these documents by posting them on a website 

  
 9 








 
maintained by the Company or by a third party under contract with the Company. If the Company posts these documents on a website, it shall notify the Optionee by email of their availability. The
Optionee acknowledges that he or she may incur costs in connection with electronic delivery, including the cost of accessing the internet and printing fees, and that an interruption of internet access may interfere with his or her ability to access
the documents. This consent shall remain in effect until this option expires or until the Optionee gives the Company written notice that it should deliver paper documents. 

(c) No Notice of Expiration Date. The Optionee agrees that the Company and its officers, employees, attorneys and agents do not have
any obligation to notify him or her prior to the expiration of this option pursuant to Section 6, regardless of whether this option will expire at the end of its full term or on an earlier date related to the termination of the Optionee’s
Service. The Optionee further agrees that he or she has the sole responsibility for monitoring the expiration of this option and for exercising this option, if at all, before it expires. This Subsection (c) shall supersede any contrary
representation that may have been made, orally or in writing, by the Company or by an officer, employee, attorney or agent of the Company. 
 SECTION 14.
DEFINITIONS. 
 (a) “Agreement” shall mean this Stock Option Agreement. 

(b) “Board of Directors” shall mean the Board of Directors of the Company, as constituted from time to time or, if a
Committee has been appointed, such Committee. 
 (c) “Cause” shall mean a good faith determination by the Board of
Directors of any of the following: 
  

	 	i.	An unauthorized use or disclosure by the Optionee of the Company’s confidential information or trade secrets, which use or disclosure causes material harm to the Company; 


 

	 	ii.	A material breach by the Optionee of any material agreement between the Purchaser and the Company; 

  

	 	iii.	A material failure by the Optionee to comply with the Company’s written policies or rules after receiving written notification of such failure from the Board of Directors; 


 

	 	iv.	The Optionee’s conviction of, or plea of “guilty” or “no contest” to, a felony under the laws of the United States or any state thereof; 


 

	 	v.	The Optionee’s gross negligence or willful misconduct in the course of performing Service; 


  
 10 









	 	vi.	A continuing failure by the Optionee to perform reasonably assigned duties after receiving written notification of such failure from the Board of Directors; or 


 

	 	vii.	A failure by the Optionee to cooperate in good faith with a governmental or internal investigation of the Company or its directors, officers or employees, if the Company has requested the Optionee’s cooperation.


 (d) “Change in Control” shall mean (i) the consummation of a merger or consolidation of the Company
with or into another entity or (ii) the sale, transfer or other disposition of all or substantially all of the Company’s assets. The foregoing notwithstanding, a merger or consolidation of the Company shall not constitute a “Change in
Control” if immediately after such merger or consolidation a majority of the voting power of the capital stock of the continuing or surviving entity, or any direct or indirect parent corporation of such continuing or surviving entity, will be
owned by persons who were the Company’s stockholders immediately prior to such merger or consolidation in substantially the same proportions as their ownership of the voting power of the Company’s capital stock immediately prior to such
merger or consolidation. 
 (e) “Code” shall mean the Internal Revenue Code of 1986, as amended. 

(f) “Committee” shall mean a committee of the Board of Directors, as described in Section 2 of the Plan. 

(g) “Company” shall mean Acacia Communications, Inc., a Delaware corporation. 

(h) “Consultant” shall mean a person who performs bona fide services for the Company, a Parent or a Subsidiary as a
consultant or advisor, excluding Employees and Outside Directors. 
 (i) “Date of Grant” shall mean the date of grant
specified in the Notice of Stock Option Grant, which date shall be the later of (i) the date on which the Board of Directors resolved to grant this option or (ii) the first day of the Optionee’s Service. 

(j) “Disability” shall mean that the Optionee is unable to engage in any substantial gainful activity by reason of any
medically determinable physical or mental impairment. 
 (k) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (l) “Exercise Price”
shall mean the amount for which one Share may be purchased upon exercise of this option, as specified in the Notice of Stock Option Grant. 

  
 11 








 (m) “Fair Market Value” shall mean the fair market value of a Share, as
determined by the Board of Directors in good faith. Such determination shall be conclusive and binding on all persons. 
 (n)
“Immediate Family” shall mean any child, stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling, mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law or sister-in-law and shall include adoptive
relationships. 
 (o) “Involuntary Termination” shall mean the termination of the Optionee’s Service by reason of:

  

	 	i.	The involuntary discharge of the Optionee by the Company (or the Parent or Subsidiary employing him) for reasons other than Cause; or 


 

	 	ii.	The voluntary resignation of the Optionee following any of the following events, if such event occurs without the consent of the Optionee (A) a change in the Optionee’s position with the Company (or the Parent
or Subsidiary employing him or her) that materially reduces his or her level of authority or responsibility (provided that the Optionee’s level of authority or responsibility shall not be deemed to be reduced merely because there are additional
employees more senior to the Optionee as a result of the Change in Control), (B) a reduction in the Optionee’s base salary by more than 10%, unless such reduction is made in connection with a commensurate reduction in the compensation of
employees of the Company generally, or (C) receipt of notice that the Optionee’s principal workplace will be relocated more than 50 miles. 


(p) “ISO” shall mean an employee incentive stock option described in Section 422(b) of the Code. 

(q) “Notice of Stock Option Grant” shall mean the document so entitled to which this Agreement is attached. 

(r) “NSO” shall mean a stock option not described in Section 422(b) or 423(b) of the Code. 

(s) “Optionee” shall mean the person named in the Notice of Stock Option Grant. 

(t) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(u) “Parent” shall mean any corporation (other than the Company) in an unbroken chain of corporations ending with the
Company, if each of the corporations other than the Company owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. 

  
 12 








 (v) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as in
effect on the Date of Grant. 
 (w) “Purchase Price” shall mean the Exercise Price multiplied by the number of Shares with
respect to which this option is being exercised. 
 (x) “Right of First Refusal” shall mean the Company’s right of
first refusal described in Section 7. 
 (y) “Securities Act” shall mean the Securities Act of 1933, as amended. 

(z) “Service” shall mean service as an Employee, Outside Director or Consultant. 

(aa) “Share” shall mean one share of Stock, as adjusted in accordance with Section 8 of the Plan (if applicable). 

(bb) “Stock” shall mean the Common Stock of the Company. 

(cc) “Subsidiary” shall mean any corporation (other than the Company) in an unbroken chain of corporations beginning with the
Company, if each of the corporations other than the last corporation in the unbroken chain owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. 

(dd) “Transferee” shall mean any person to whom the Optionee has directly or indirectly transferred any Share acquired under
this Agreement. 
 (ee) “Transfer Notice” shall mean the notice of a proposed transfer of Shares described in
Section 7. 

  
 13 








 STOCK OPTION AMENDMENT AGREEMENT 

This STOCK OPTION AMENDMENT AGREEMENT by and between Acacia Communications, Inc., a Delaware corporation (the “Company”) and
[                    ] (the “Optionee”) is made as of [            ],
2015 (this “Agreement”). 
 WHEREAS, the Company and the Optionee are parties to (i) a Notice of Grant and
Stock Option Agreement dated as of [            ] 2      , (“Option Agreement”), pursuant to which the Optionee was granted an option to
purchase [                ] shares of the Company’s Common Stock (the “Option”); 

WHEREAS, the Company seeks to provide certain accelerated vesting terms upon a change in control to the Optionee; and 

WHEREAS, the Optionee hereby agrees to amend the Option Agreement in order to modify the provisions regarding vesting as set forth
herein. 
 NOW, THEREFORE, in consideration of the foregoing, the parties hereby agree as follows: 

1. Amendment of Option Agreement. 

(a) Section 2(a) of the Option Agreement is hereby amended and restated in its entirety to read as follows: 

“Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or
part of this option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, if the Company is subject to a Change in Control before the Optionee’s Service terminates, then at all
times after the Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service.” 







 (b) Section [14] of the Option Agreement is hereby amended by inserting the following definitions
immediately after the definition of “Board of Directors”: 
 “Change in Control” shall mean
(i) the consummation of a merger or consolidation of the Company with or into another entity or (ii) the sale, transfer or other disposition of all or substantially all of the Company’s assets. The foregoing notwithstanding, a merger
or consolidation of the Company shall not constitute a “Change in Control” if immediately after such merger or consolidation a majority of the voting power of the capital stock of the continuing or surviving entity, or any direct or
indirect parent corporation of such continuing or surviving entity, will be owned by persons who were the Company’s stockholders immediately prior to such merger or consolidation in substantially the same proportions as their ownership of the
voting power of the Company’s capital stock immediately prior to such merger or consolidation.” 
 (c) Section [14] of the Option
Agreement is hereby amended by renumbering the definitions listed therein to reflect the amendments set forth in Section 1(b) hereof. 

2. Effective Date. This Agreement will become effective as of the date set forth above. 

3. Counterparts. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument. 
 4. Effect of Amendment to the Option Agreement. Except as amended
hereby, all of the terms of the Option Agreement shall remain and continue in full force and effect. 
 (REMAINDER OF PAGE INTENTIONALLY
BLANK) 







 IN WITNESS WHEREOF, the parties have executed this Stock Option Amendment Agreement as of the
date first above written above. 
  

			
	ACACIA COMMUNICATIONS, INC.
		
	By:	 	  

	Name:	 	  

	Title:	 	  




 

			
	OPTIONEE
	
	  

	Printed Name:	 	  



 SIGNATURE PAGE 

TO STOCK OPTION AMENDMENT AGREEMENT 







 STOCK OPTION AMENDMENT AGREEMENT 

This STOCK OPTION AMENDMENT AGREEMENT by and between Acacia Communications, Inc., a Delaware corporation (the “Company”) and
[                    ] (the “Optionee”) is made as of [            ],
2015 (this “Agreement”). 
 WHEREAS, the Company and the Optionee are parties to (i) a Notice of Grant and
Stock Option Agreement dated as of [            ] 2      , (“Option Agreement”), pursuant to which the Optionee was granted an option to
purchase [                ] shares of the Company’s Common Stock (the “Option”); 

WHEREAS, the Company seeks to provide certain accelerated vesting terms upon a change in control to the Optionee; and 

WHEREAS, the Optionee hereby agrees to amend the Option Agreement in order to modify the provisions regarding vesting as set forth
herein. 
 NOW, THEREFORE, in consideration of the foregoing, the parties hereby agree as follows: 

1. Amendment of Option Agreement. 

(a) Section 2(a) of the Option Agreement is hereby amended and restated in its entirety to read as follows: 

“Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or
part of this option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, the following rules shall apply if the Company is subject to a Change in Control before the Optionee’s
Service terminates: 
  

	 	i.	At all times after a Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service. 


 

	 	ii.	If the Optionee is subject to an Involuntary Termination upon or after the Change in Control, then this option shall vest in full and become immediately exercisable.” 


(b) Section [14] of the Option Agreement is hereby amended by inserting the following definitions immediately after the definition of
“Board of Directors”: 
 “Cause” shall mean a good faith determination by the Board of Directors
of any of the following: 
  

	 	i.	An unauthorized use or disclosure by the Optionee of the Company’s confidential information or trade secrets, which use or disclosure causes material harm to the Company; 









	 	ii.	A material breach by the Optionee of any material agreement between the Purchaser and the Company; 

  

	 	iii.	A material failure by the Optionee to comply with the Company’s written policies or rules after receiving written notification of such failure from the Board of Directors; 


 

	 	iv.	The Optionee’s conviction of, or plea of “guilty” or “no contest” to, a felony under the laws of the United States or any state thereof; 


 

	 	v.	The Optionee’s gross negligence or willful misconduct in the course of performing Service; 

  

	 	vi.	A continuing failure by the Optionee to perform reasonably assigned duties after receiving written notification of such failure from the Board of Directors; or 


 

	 	vii.	A failure by the Optionee to cooperate in good faith with a governmental or internal investigation of the Company or its directors, officers or employees, if the Company has requested the Optionee’s cooperation.


 “Change in Control” shall mean (i) the consummation of a merger or consolidation of
the Company with or into another entity or (ii) the sale, transfer or other disposition of all or substantially all of the Company’s assets. The foregoing notwithstanding, a merger or consolidation of the Company shall not constitute a
“Change in Control” if immediately after such merger or consolidation a majority of the voting power of the capital stock of the continuing or surviving entity, or any direct or indirect parent corporation of such continuing or surviving
entity, will be owned by persons who were the Company’s stockholders immediately prior to such merger or consolidation in substantially the same proportions as their ownership of the voting power of the Company’s capital stock immediately
prior to such merger or consolidation.” 
 (c) Section [14] of the Option Agreement is hereby amended by inserting the following
definitions immediately after the definition of “Immediate Family”: 
 “Involuntary Termination”
shall mean the termination of the Optionee’s Service by reason of: 
  

	 	i.	The involuntary discharge of the Optionee by the Company (or the Parent or Subsidiary employing him) for reasons other than Cause; or 


 

	 	ii.	 The voluntary resignation of the Optionee following any of the following events, if such event occurs without the consent of the Optionee (A) a
change in the Optionee’s position with the Company (or the Parent or Subsidiary 










	 	
employing him or her) that materially reduces his or her level of authority or responsibility (provided that the Optionee’s level of authority or responsibility shall not be deemed to be
reduced merely because there are additional employees more senior to the Optionee as a result of the Change in Control), (B) a reduction in the Optionee’s base salary by more than 10%, unless such reduction is made in connection with a
commensurate reduction in the compensation of employees of the Company generally, or (C) receipt of notice that the Optionee’s principal workplace will be relocated more than 50 miles. 


(d) Section [14] of the Option Agreement is hereby amended by renumbering the definitions listed therein to reflect the amendments set forth
in Sections 1(b) through 1(c) hereof. 
 2. Effective Date. This Agreement will become effective as of the date set forth above. 

3. Counterparts. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument. 
 4. Effect of Amendment to the Option Agreement. Except as amended
hereby, all of the terms of the Option Agreement shall remain and continue in full force and effect. 
 (REMAINDER OF PAGE INTENTIONALLY
BLANK) 







 IN WITNESS WHEREOF, the parties have executed this Stock Option Amendment Agreement as of the
date first above written above. 
  

			
	ACACIA COMMUNICATIONS, INC.
		
	By:	 	  

	Name:	 	  

	Title:	 	  

	
	OPTIONEE


 
			
	
	  

	Printed Name:	 	  



 SIGNATURE PAGE 

TO STOCK OPTION AMENDMENT AGREEMENT